7Baggers

Brookline Bancorp, Inc
(NASDAQ:BRKL) 

BRKL stock logo

Brookline Bancorp, Inc. operates as a bank holding company for the Brookline Bank that provide commercial, business, and retail banking services to corporate, municipal, and retail customers in the United States. Its deposit products include non-interest-bearing demand checking, NOW, savings, and mo...

Full Time Employees: 763
Sector: Financial Services
Industry: Banks-Regional

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At a glance:
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Quarterly
Annual
    Unit: USD2025-06-30 2025-03-31 2024-12-31 2024-09-30 2024-06-30 2024-03-31 2023-12-31 2023-09-30 2023-06-30 2023-03-31 2022-12-31 2022-09-30 2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-06-30 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2016-12-31 2016-09-30 2016-03-31 2015-06-30 2014-09-30 2014-06-30 2013-03-31 2012-06-30 2012-03-31 2011-09-30 2011-06-30 2011-03-31 2010-09-30 2010-06-30 2009-12-31 2009-09-30 2009-06-30 2009-03-31 2008-06-30 2008-03-31 2007-09-30 2007-06-30 2007-03-31 2006-06-30 2006-03-31 2005-12-31 2005-09-30 2005-06-30 2005-03-31 2004-09-30 2004-06-30 2004-03-31 2003-09-30 2003-06-30 2003-03-31 2002-09-30 2002-06-30 2002-03-31 2001-09-30 
                                                                       
      interest and dividend income:
                                                                       
      loans and leases
    143,933,000 143,309,000 147,436,000 149,643,000 145,585,000 145,265,000 142,948,000 136,561,000 132,299,000 121,931,000 98,386,000 84,375,000 74,287,000 71,721,000 73,560,000 74,332,000 75,026,000 75,009,000 76,583,000 76,240,000 77,416,000 79,559,000 82,798,000 75,877,000 73,329,000 67,272,000 64,272,000 63,054,000 57,247,000 57,858,000 54,247,000 51,684,000 51,769,000 50,433,000 49,419,000 50,135,000 49,643,000                               
      debt securities
    6,691,000 6,765,000 6,421,000 6,473,000 6,480,000 6,878,000 6,945,000 6,799,000 8,034,000 7,870,000 3,497,000 3,337,000 3,249,000 2,996,000 2,972,000 2,967,000 3,121,000 3,118,000 3,335,000 3,746,000 3,701,000 2,976,000 3,158,000 3,585,000 3,563,000 3,323,000 3,214,000 3,154,000 2,881,000 2,822,000 2,932,000 2,931,000 2,312,000 2,360,000 1,852,000 1,541,000 3,229,000 1,487,000 1,754,000 1,757,000 1,927,000 1,960,000 2,141,000 2,528,000 2,845,000 3,076,000 3,740,000 3,416,000 3,342,000 3,560,000 3,780,000 3,640,000 3,620,000 3,334,000 2,876,000 2,644,000 2,267,000 1,427,000 1,942,000 1,506,000 1,750,000 910,000 3,253,000 2,455,000 2,560,000 2,309,000 2,511,000 
      restricted equity securities
    1,062,000 1,203,000 1,460,000 1,458,000 1,376,000 1,492,000 1,333,000 1,310,000 1,673,000 1,255,000                                 2,000 2,000 2,000  326,000 407,000 469,000 403,000 481,000 2,000 309,000 281,000 241,000 239,000 219,000 139,000 71,000 70,000 71,000 71,000 77,000 87,000 87,000 83,000 126,000 
      short-term investments
    2,386,000 2,451,000 2,830,000 1,986,000 1,914,000 1,824,000 1,093,000 2,390,000 3,351,000 1,495,000 754,000 464,000 156,000 66,000 88,000 83,000 42,000 39,000 59,000 46,000 99,000 209,000 351,000 145,000 179,000 120,000 100,000 180,000 93,000 47,000 39,000 60,000 15,000 14,000 31,000 68,000 27,000 28,000 26,000 24,000 32,000 29,000 32,000 48,000 46,000 202,000 405,000 1,007,000 1,759,000 1,798,000 1,684,000 1,326,000 1,112,000 1,241,000 1,259,000 1,009,000 846,000 401,000 305,000 298,000 288,000 350,000 577,000 1,723,000 462,000 351,000 257,000 
      total interest and dividend income
    154,072,000 153,728,000 158,147,000 159,560,000 155,355,000 155,459,000 152,319,000 147,060,000 145,357,000 132,551,000 103,403,000 88,643,000 78,029,000 75,111,000 76,945,000 77,695,000 78,422,000 78,467,000 80,467,000 80,704,000 82,124,000 83,522,000 87,184,000 80,636,000 78,074,000 71,639,000 68,337,000 67,176,000 60,983,000 61,531,000 57,898,000 55,166,000 54,616,000 53,346,000 51,612,000 51,839,000 52,991,000                               
      interest expense:
                                                                       
      deposits
    52,682,000 53,478,000 56,562,000 59,796,000 59,721,000 56,884,000 54,034,000 49,116,000 43,147,000 29,368,000 14,185,000 7,354,000 4,282,000 3,771,000 4,055,000 4,571,000 5,380,000 6,707,000 8,825,000 10,583,000 12,778,000 16,240,000 17,712,000 11,916,000 9,219,000 7,099,000 6,681,000 5,984,000 5,195,000 5,112,000 4,745,000 4,296,000 4,248,000 4,201,000 4,834,000 5,463,000 5,517,000 4,971,000 5,138,000 4,895,000 5,096,000 5,348,000 6,532,000 7,300,000         7,446,000 7,101,000 6,159,000 5,354,000 4,559,000 2,975,000 2,832,000 2,697,000 2,860,000 3,224,000 3,442,000 3,946,000 4,091,000 4,076,000 5,694,000 
      borrowed funds
    12,705,000 14,420,000 16,597,000 16,756,000 15,633,000 16,987,000 14,730,000 13,874,000 16,173,000 17,134,000 9,188,000 3,263,000 1,880,000 1,492,000 1,429,000 2,427,000 1,936,000 2,651,000 3,417,000 4,183,000 5,058,000 5,570,000 6,338,000 6,388,000 6,138,000 5,049,000 3,999,000 4,349,000 3,934,000 4,069,000 3,950,000 3,698,000 3,044,000 2,711,000    2,671,000 2,685,000 2,608,000 3,087,000 3,699,000 4,522,000 5,247,000 6,151,000  6,600,000 6,203,000 6,211,000 5,704,000 5,456,000 6,213,000 4,843,000 4,144,000 3,994,000 3,672,000 3,382,000 2,477,000 2,174,000 2,139,000 1,608,000 1,409,000 1,421,000 2,675,000 2,666,000 2,604,000 2,503,000 
      total interest expense
    65,387,000 67,898,000 73,159,000 76,552,000 75,354,000 73,871,000 68,764,000 62,990,000 59,320,000 46,502,000 23,373,000 10,617,000 6,162,000 5,263,000 5,484,000 6,998,000 7,316,000 9,358,000 12,242,000 14,766,000 17,836,000 21,810,000 24,050,000 18,304,000 15,357,000 12,148,000 10,680,000 10,333,000 9,129,000 9,181,000 8,695,000 7,994,000 7,292,000 6,912,000 7,943,000 9,080,000 9,357,000 7,642,000 7,823,000 7,503,000 8,183,000 9,047,000 11,055,000 12,547,000 14,406,000 15,748,000 17,332,000 18,691,000 18,846,000 18,046,000 17,434,000 15,460,000 12,496,000 11,446,000 10,335,000 9,194,000 8,076,000 5,452,000 5,006,000 4,836,000 4,468,000 4,633,000 4,863,000 6,621,000 6,757,000 6,680,000 8,197,000 
      net interest income
    88,685,000 85,830,000 84,988,000 83,008,000 80,001,000 81,588,000 83,555,000 84,070,000 86,037,000 86,049,000 80,030,000 78,026,000 71,867,000 69,848,000 71,461,000 70,697,000 71,106,000 69,109,000 68,225,000 65,938,000 64,288,000 61,712,000 63,134,000 62,332,000 62,717,000 59,491,000 57,657,000 56,843,000 51,854,000 52,350,000 49,203,000 47,172,000 47,324,000 46,434,000 43,669,000 42,759,000 43,634,000 27,644,000 27,629,000 25,706,000 24,268,000 23,728,000 22,605,000 21,775,000 21,816,000 19,106,000 18,046,000 17,196,000 17,997,000 18,051,000 18,133,000 17,689,000 16,628,000 16,913,000 16,949,000 17,130,000 17,054,000 12,661,000 12,887,000 12,175,000 12,141,000 10,712,000 12,423,000 12,011,000 10,929,000 10,671,000 10,862,000 
      provision for credit losses on loans
    6,997,000 5,974,000 4,141,000 4,832,000 5,607,000 7,423,000                                                              
      provision (recovery) of credit losses on investments
    3,000 12,000                                                                  
      net interest income after provision for credit losses
    81,685,000 79,844,000 80,951,000 78,348,000 74,433,000 74,209,000 79,780,000 81,039,000 80,178,000 60,507,000                                                          
      non-interest income:
                                                                       
      deposit fees
    2,472,000 2,361,000 2,297,000 2,353,000 3,001,000 2,897,000 3,064,000 3,024,000 2,866,000 2,657,000 2,916,000 2,759,000 2,744,000 2,500,000 2,653,000 2,629,000 3,015,000 2,281,000 2,358,000 2,305,000 1,929,000 2,458,000 2,680,000 2,648,000 2,620,000 2,463,000 2,542,000 2,547,000 2,263,000 2,289,000 2,145,000 2,195,000 2,352,000 2,204,000                                  
      loan fees
    472,000 393,000 439,000 464,000 702,000 789,000 515,000 639,000 491,000 391,000 446,000 349,000 666,000 747,000 448,000 487,000 607,000 599,000 588,000 397,000 513,000 550,000 398,000 417,000 330,000 290,000 338,000 282,000 322,000 330,000 330,000 271,000 601,000 124,000                                  
      loan level derivative income
    -4,000 70,000 1,115,000  106,000 437,000 778,000 376,000 363,000 2,373,000 670,000 1,275,000 1,615,000 686,000 3,981,000 218,000 7,000 474,000 145,000 527,000 1,440,000 2,156,000 1,772,000 2,192,000 571,000 866,000 755,000 844,000 265,000 858,000 1,629,000 941,000                                    
      gain on sales of loans and leases held-for-sale
    264,000 24,000 136,250 415,000 130,000  542,750 225,000 308,000 1,638,000 381,000 889,000 291,000 344,000 451,000 557,000 538,000 709,000 67,000 632,000 299,000 120,000 561,000 535,000 722,000 299,000 935,000 1,049,000   905,000 279,000 538,000 54,000                                  
      other
    2,766,000 2,812,000 2,330,000 3,116,000 2,457,000 2,161,000 3,260,000 1,244,000 1,431,000 4,177,000 2,091,000 1,562,000 1,612,000 1,252,000 1,716,000 1,695,000 1,742,000 738,000 1,061,000 947,000 1,468,000 2,714,000 1,710,000 1,277,000 1,283,000 1,088,000 1,245,000 1,251,000 1,344,000 1,264,000 1,460,000 1,181,000 2,710,000 1,466,000 3,260,000 3,056,000 2,514,000 1,471,000 1,649,000 1,349,000 1,245,000 1,362,000 1,144,000 1,410,000 1,478,000 1,307,000 1,484,000 1,264,000 1,243,000 1,172,000 1,093,000 1,231,000 675,000 -2,659,000 1,263,000 954,000 590,000 625,000 636,000 607,000 701,000 751,000 591,000 538,000 386,000 486,000 456,000 
      total non-interest income
    5,970,000 5,660,000 6,587,000 6,348,000 6,396,000 6,284,000 8,027,000 5,508,000 5,462,000 12,937,000 9,056,000 6,834,000 6,928,000 5,529,000 10,699,000 5,586,000 5,910,000 4,794,000 4,219,000 4,862,000 6,235,000 9,328,000 7,478,000 7,069,000 5,526,000 6,168,000 5,815,000 5,973,000 4,300,750 5,329,000 6,469,000  5,656,000 3,290,000 3,327,000 4,721,000 3,595,000 1,232,000 1,687,000 1,360,000 372,000 1,053,000 819,000 995,000 651,000 292,000 1,123,000  927,000 1,281,000 1,049,000 910,000 1,200,000 1,173,000 928,000 1,578,000 1,619,000 1,494,000 1,229,000 1,881,000 805,000 1,094,000 960,000 373,000 801,000 1,504,000 1,272,000 
      non-interest expense:
                                                                       
      compensation and employee benefits
    35,147,000 35,853,000 37,202,000 35,130,000 34,762,000 36,629,000 35,401,000 33,491,000 33,438,000 36,565,000 29,525,000 28,306,000 28,772,000 26,884,000 28,598,000 27,206,000 25,161,000 25,821,000 25,054,000 26,092,000 24,619,000 25,219,000 23,953,000 22,338,000 22,565,000 22,314,000 20,652,000 21,067,000 19,657,000 20,369,000 18,727,000 17,085,000 18,258,000 17,295,000 16,298,000 14,238,000 14,688,000 8,091,000 7,795,000 6,811,000 5,895,000 5,482,000 5,102,000 5,195,000 5,294,000 4,966,000 5,210,000 5,348,000 5,227,000 5,246,000 5,239,000 5,089,000 4,177,000 3,375,000 3,332,000 3,328,000 3,950,000 2,477,000 2,537,000 2,535,000 2,439,000 2,422,000 2,392,000 2,147,000 2,131,000 2,082,000 2,200,000 
      occupancy
    5,349,000 5,721,000 5,393,000 5,343,000 5,551,000 5,769,000 5,127,000 4,983,000 4,870,000 5,223,000 4,005,000 3,906,000 3,807,000 4,284,000 3,558,000 3,567,000 3,832,000 4,004,000 3,806,000 3,802,000 3,825,000 3,953,000 3,752,000 3,913,000 3,879,000 3,959,000 3,594,000 3,650,000 3,554,000 3,411,000 3,526,000 3,437,000 3,334,000 3,154,000 3,083,000 2,503,000 2,676,000 1,637,000 1,499,000 1,374,000 1,128,000 1,144,000 924,000 1,015,000 1,094,000 1,045,000 905,000 934,000 854,000 836,000 855,000 766,000 793,000 707,000 721,000 685,000 704,000 399,000 374,000 417,000 360,000 443,000 337,000 304,000 275,000 287,000 295,000 
      equipment and data processing
    6,841,000 7,012,000 6,780,000 6,831,000 6,732,000 7,031,000 7,245,000 6,766,000 6,531,000 6,462,000 5,758,000 5,066,000 4,931,000 5,078,000 4,576,000 4,556,000 4,697,000 4,493,000 4,193,000 4,293,000 4,155,000 4,703,000 4,641,000 4,601,000 4,368,000 4,618,000 4,417,000 4,210,000 4,028,000 3,826,000 3,714,000 3,680,000 4,193,000 4,348,000 3,861,000 3,632,000 3,645,000 2,362,000 2,290,000 2,075,000 1,874,000 1,886,000 1,763,000 1,868,000 1,870,000 1,750,000 1,676,000 1,698,000 1,700,000 1,653,000 1,520,000 1,522,000 1,417,000 1,371,000 1,361,000 1,596,000 1,591,000 1,164,000 1,091,000 993,000 879,000 776,000 627,000 654,000 680,000 703,000 898,000 
      professional services
    1,471,000 1,726,000 1,345,000 2,143,000 1,745,000 1,900,000 1,442,000 2,368,000 1,986,000 1,430,000 1,546,000 1,069,000 1,219,000 1,226,000 1,151,000 1,072,000 1,245,000 1,226,000 1,338,000 1,112,000 1,056,000 1,651,000 1,087,000 1,075,000 1,055,000 1,144,000 1,200,000 973,000 927,000 997,000 966,000 1,163,000 1,001,000 1,487,000 1,501,000 2,554,000 6,453,000 1,406,000 1,458,000 789,000 668,000 995,000 707,000 566,000 576,000 645,000 519,000 486,000 462,000 536,000 479,000  311,000    349,000           
      fdic insurance
    1,880,000 2,037,000 2,017,000 2,118,000 2,025,000 1,884,000 1,839,000 2,152,000 2,609,000 1,244,000 1,001,000 709,000 739,000 728,000 617,000 662,000 657,000 1,044,000 1,630,000 1,363,000 858,000 378,000 745,000 846,000 514,000 635,000 678,000 842,000 655,000 956,000 878,000 831,000 873,000 847,000 934,000 671,000 630,000 536,000 324,000 434,000 418,000 411,000 415,000 435,000 1,573,000                       
      advertising and marketing
    1,371,000 868,000 1,303,000 859,000 1,504,000 1,574,000 758,000 1,174,000 1,382,000 1,410,000 1,052,000 1,337,000 1,319,000 1,272,000 880,000 1,077,000 1,110,000 1,100,000 1,010,000 1,024,000 1,017,000 1,075,000 1,112,000 1,068,000 1,118,000 1,057,000 856,000 839,000 823,000 844,000 861,000 823,000 745,000 776,000 670,000 774,000 703,000 414,000 407,000 321,000 359,000 412,000 297,000 283,000 286,000 131,000 203,000 135,000 406,000 279,000 141,000 269,000 187,000 287,000 352,000 251,000 204,000 113,000 189,000 187,000 188,000 188,000 187,000 187,000 175,000 162,000 238,000 
      amortization of identified intangible assets
    1,431,000 1,430,000 1,701,000 1,668,000 1,669,000 1,708,000 1,965,000 1,955,000 1,954,000 1,966,000 120,000 120,000 120,000 134,000 208,000 208,000 228,000 232,000 312,000 312,000 311,000 336,000 420,000 537,000 539,000 467,000 519,000 519,000 621,000 623,000 635,000 724,000 828,000 827,000 1,165,000 1,271,000 1,283,000 443,000 455,000 296,000 306,000 306,000 372,000 372,000 372,000 372,000 438,000 438,000   503,000                 
      merger and restructuring expense
    439,000 971,000 3,378,000  823,000                                                               
      total non-interest expense
    58,061,000 60,022,000 63,719,000 57,948,000 59,184,000 61,014,000 59,244,000 57,679,000 57,825,000 64,776,000 47,225,000 44,959,000 44,871,000 42,487,000 42,909,000 40,922,000 37,966,000 40,811,000 40,038,000 40,947,000 39,109,000 40,748,000 39,604,000 37,310,000 37,702,000 39,938,000 35,152,000 35,408,000 32,641,000 33,388,000 32,053,000 30,452,000 31,924,000 31,222,000 30,772,000 28,699,000 32,592,000 17,079,000 15,877,000 13,449,000 11,893,000 11,998,000 10,724,000 11,144,000 12,543,000 10,720,000 10,435,000 10,303,000 10,395,000 10,226,000 9,830,000 9,446,000 8,255,000 8,033,000 8,630,000 8,569,000 8,726,000 5,859,000 5,545,000 5,841,000 4,928,000 4,580,000 4,134,000 3,830,000 3,647,000 3,720,000 4,129,000 
      income before provision for income taxes
    29,594,000 25,482,000 23,819,000 26,748,000 21,645,000 19,479,000 28,563,000 28,868,000 27,815,000 8,668,000                                                          
      provision for income taxes
    7,568,000 6,382,000 6,283,000 6,606,000 5,273,000 4,814,000 5,675,000 6,167,000 5,965,000 1,108,000                                                          
      net income
    22,026,000 19,100,000 17,536,000 20,142,000 16,372,000 14,665,000 22,888,000 22,701,000 21,850,000 7,560,000 29,695,000 30,149,000 25,195,000 24,705,000 21,723,750 28,839,000 31,602,000 26,454,000                  7,783,000 6,634,000 6,582,000 7,327,000 7,550,000 7,273,000 7,246,000 6,019,000 5,430,000 4,803,000 3,483,000 3,674,000 2,694,000 4,249,000 4,852,000 4,941,000 4,929,000 5,397,000 5,536,000 5,521,000 5,441,000 5,532,000 4,497,000 4,622,000 4,652,000 4,502,000 6,687,000 -148,000 5,461,000 5,131,000 5,478,000 4,929,000 
      yoy
    34.53% 30.24% -23.38% -11.27% -25.07% 93.98% -22.92% -24.70% -13.28% -69.40% 36.69% 4.54% -20.27% -6.61%                      3.09% -8.79% -9.16% 21.73% 39.04% 51.43% 108.04% 63.83% 101.56% 13.04% -28.22% -25.64% -45.34% -21.27% -12.36% -10.51% -9.41% -2.44% 23.10% 19.45% 16.96% 22.88% -32.75% -3222.97% -14.81% -12.26% 22.07% -103.00%     
      qoq
    15.32% 8.92% -12.94% 23.03% 11.64% -35.93% 0.82% 3.89% 189.02% -74.54% -1.51% 19.66% 1.98% 13.72% -24.67% -8.74% 19.46%                   17.32% 0.79% -10.17% -2.95% 3.81% 0.37% 20.39% 10.85% 13.05% 37.90% -5.20% 36.38% -36.60% -12.43% -1.80% 0.24% -8.67% -2.51% 0.27% 1.47% -1.64% 23.02% -2.70% -0.64% 3.33% -32.68% -4618.24% -102.71% 6.43% -6.33% 11.14%  
      earnings per common share:
                                                                       
      basic
    250 210 190 230 180 160 260 260 250 90 380 390 330 320 370 370 400 340 330 240 250 -220 260 280 260 240 90 200 180 190 180  170 140 130 110 90 110 120 120 120 120 100 90 80 60 60 50 70 80 80 80 90 100 90 90 90 80 80 80 80 120  90 190 210 180 
      diluted
    250 210 200 230 180 160 260 260 250 90 380 390 330 320 370 370 400 340 330 240 250 -220 260 280 260 240 90 200 180 190 180  170 140 130 110 90 110 120 120 120 120 100 90 80 60 60 50 70 80 80 80 90 90 90 90 90 80 80 80 80 120  90 190 210 180 
      weighted-average common shares outstanding:
                                                                       
      basic
    89,104,605,000 89,103,510,000 88,983,248,000 89,033,463,000 88,904,692,000 88,894,577,000 88,230,681,000 88,795,270,000 88,665,135,000 86,563,641,000 77,079,278,000 76,779,038,000 77,091,013,000 77,617,227,000 77,974,851,000 78,000,261,000 78,150,364,000 78,143,752,000 78,951,892,000 78,948,139,000 78,849,282,000 79,481,462,000 79,669,922,000 80,315,050,000 80,184,977,000 77,879,593,000 74,459,508,000 76,452,539,000 70,261,954,000 70,299,722,000 70,186,921,000 70,049,829,000 69,989,909,000 69,886,576,000 69,762,784,000 69,677,656,000 69,664,619,000 58,640,775,000 58,629,265,000 58,611,488,000 58,586,274,000 58,574,230,000 58,370,569,000 58,522,547,000 58,491,808,000 57,919,412,000 57,571,596,000 57,488,499,000 58,541,627,000 59,749,897,000 60,534,234,000 60,363,461,000 60,309,532,000 60,054,059,000 60,108,206,000 60,086,614,000 59,944,866,000 57,373,970,000 57,247,354,000 57,076,261,000 56,644,208,000 56,599,521,000 57,468,369,000 57,583,175,000 26,306,216,000 26,272,049,000 26,778,953,000 
      diluted
    89,612,781,000 89,567,747,000 89,302,304,000 89,319,611,000 89,222,315,000 89,181,508,000 88,450,646,000 88,971,210,000 88,926,543,000 86,837,806,000 77,351,834,000 77,007,971,000 77,419,288,000 77,926,822,000 78,243,416,000 78,240,633,000 78,470,451,000 78,404,063,000 79,103,289,000 79,055,901,000 79,015,274,000 79,665,774,000 79,886,292,000 80,515,467,000 80,505,614,000 78,167,800,000 74,811,408,000 76,759,430,000 70,444,083,000 70,450,760,000 70,343,408,000 70,215,850,000 70,088,987,000 70,012,377,000 69,830,630,000 69,715,890,000 69,665,873,000 58,640,973,000 58,630,908,000 58,618,309,000 58,588,536,000 58,579,529,000 58,407,467,000 58,529,929,000 58,495,557,000 58,052,757,000 57,821,388,000 57,763,871,000 59,020,681,000 60,346,901,000 61,182,972,000 61,082,113,000 61,051,157,000 60,836,211,000 60,948,961,000 60,866,872,000 60,737,986,000 58,144,811,000  58,055,753,000 57,658,817,000 57,575,487,000 57,468,369,000 58,624,026,000 26,990,303,000 26,708,550,000 27,161,553,000 
      dividends paid per common share
    135 135 101.25 135 135 135 101.25 135 135 135 96.25 130 130 125 88.75 120 120 115 86.25 115 115 115 110                                             
      provision (credit) for credit losses on investments
      -63,750 -172,000 -39,000 -44,000                                                              
      gain on investment securities
            3,000 1,701,000     -32,000  1,000 -7,000  54,000 586,000 1,330,000 357,000                                             
      merger and acquisition expense
            1,002,000 6,409,000 641,000 1,073,000 535,000           22,000 334,000 2,905,000 206,000 205,000                                        
      weighted-average common shares outstanding during the year:
                                                                       
      basic
    89,104,605,000 89,103,510,000 88,983,248,000 89,033,463,000 88,904,692,000 88,894,577,000 88,230,681,000 88,795,270,000 88,665,135,000 86,563,641,000 77,079,278,000 76,779,038,000 77,091,013,000 77,617,227,000 77,974,851,000 78,000,261,000 78,150,364,000 78,143,752,000 78,951,892,000 78,948,139,000 78,849,282,000 79,481,462,000 79,669,922,000 80,315,050,000 80,184,977,000 77,879,593,000 74,459,508,000 76,452,539,000 70,261,954,000 70,299,722,000 70,186,921,000 70,049,829,000 69,989,909,000 69,886,576,000 69,762,784,000 69,677,656,000 69,664,619,000 58,640,775,000 58,629,265,000 58,611,488,000 58,586,274,000 58,574,230,000 58,370,569,000 58,522,547,000 58,491,808,000 57,919,412,000 57,571,596,000 57,488,499,000 58,541,627,000 59,749,897,000 60,534,234,000 60,363,461,000 60,309,532,000 60,054,059,000 60,108,206,000 60,086,614,000 59,944,866,000 57,373,970,000 57,247,354,000 57,076,261,000 56,644,208,000 56,599,521,000 57,468,369,000 57,583,175,000 26,306,216,000 26,272,049,000 26,778,953,000 
      diluted
    89,612,781,000 89,567,747,000 89,302,304,000 89,319,611,000 89,222,315,000 89,181,508,000 88,450,646,000 88,971,210,000 88,926,543,000 86,837,806,000 77,351,834,000 77,007,971,000 77,419,288,000 77,926,822,000 78,243,416,000 78,240,633,000 78,470,451,000 78,404,063,000 79,103,289,000 79,055,901,000 79,015,274,000 79,665,774,000 79,886,292,000 80,515,467,000 80,505,614,000 78,167,800,000 74,811,408,000 76,759,430,000 70,444,083,000 70,450,760,000 70,343,408,000 70,215,850,000 70,088,987,000 70,012,377,000 69,830,630,000 69,715,890,000 69,665,873,000 58,640,973,000 58,630,908,000 58,618,309,000 58,588,536,000 58,579,529,000 58,407,467,000 58,529,929,000 58,495,557,000 58,052,757,000 57,821,388,000 57,763,871,000 59,020,681,000 60,346,901,000 61,182,972,000 61,082,113,000 61,051,157,000 60,836,211,000 60,948,961,000 60,866,872,000 60,737,986,000 58,144,811,000  58,055,753,000 57,658,817,000 57,575,487,000 57,468,369,000 58,624,026,000 26,990,303,000 26,708,550,000 27,161,553,000 
      provision for credit losses
          8,504,250 2,947,000 5,726,000                                                           
      provision for investment losses
          103,750 84,000 133,000                                                           
      provision (credit) for credit losses
             25,542,000 5,725,000 2,835,000 173,000                                                       
      marketable and restricted equity securities
              766,000 467,000 337,000 328,000 325,000 313,000 233,000 301,000 490,000 672,000 908,000 778,000 877,000 1,029,000 1,003,000 924,000 751,000 788,000 762,000 804,000 680,000 491,000 520,000 539,000 310,000 95,000 92,000                               
      net interest income after benefit from credit losses
              54,209,750 75,191,000 71,640,000 70,008,000 70,710,000 73,807,000 74,437,000 71,256,000 70,328,000 61,410,000 58,941,000 7,598,000 59,377,000 59,615,000 61,247,000 58,850,000 55,855,000 53,932,000 48,639,000 50,135,000 46,825,000 45,259,000 45,290,000 44,158,000 41,814,000 36,081,000 40,387,000 26,753,000 26,790,000 24,647,000 23,717,000 23,067,000 19,975,000 19,302,000 19,940,000 16,305,000 15,467,000 15,082,000                    
      loss on investment securities
                                                                       
      income before benefit from income taxes
              25,953,250 37,066,000 33,697,000 33,050,000 38,500,000 38,471,000 42,381,000 35,239,000 34,509,000 25,325,000 26,067,000 -23,822,000 27,251,000 29,374,000 29,071,000 25,080,000 26,518,000 24,497,000 16,038,500 22,076,000 21,241,000  19,022,000 16,226,000                                  
      benefit from income taxes
              5,941,000 6,917,000 8,502,000 8,345,000     7,846,000 6,646,000   6,780,000 6,140,000 7,342,000 5,652,000 18,712,000 8,330,000 5,717,000 7,804,000 7,599,000  6,779,000 5,774,000 5,129,000 4,320,000 4,756,000 4,324,000 5,273,000 5,008,000 4,923,000 4,876,000 4,051,000 3,723,000 3,245,000 2,394,000 2,417,000 1,748,000 2,711,000 3,103,000 3,118,000 3,298,000 3,428,000 3,677,000 3,694,000 3,741,000 3,761,000 3,164,000 3,238,000 3,233,000 3,276,000 2,906,000 3,507,000 3,143,000 2,952,000 3,077,000 2,801,000 
      benefit from investment losses
                54,000 4,000                                                      
      (credit) benefit from credit losses
                 -164,000 751,000 -3,110,000 -3,331,000 -2,147,000                                                  
      benefit for income taxes
                  7,299,000 9,632,000 10,779,000 8,785,000   6,496,000 -6,546,000                                              
      benefit from credit losses
                      -2,103,000 4,528,000 5,347,000 54,114,000 3,757,000 2,717,000 1,470,000 641,000 1,802,000 2,911,000 3,215,000 2,215,000 2,378,000 1,913,000 2,034,000 2,276,000 1,855,000 6,678,000 3,247,000 891,000 839,000 1,059,000 551,000 661,000 2,630,000 2,473,000 1,876,000 2,801,000 2,579,000 2,114,000                    
      net income before noncontrolling interest in subsidiary
                      26,663,000 18,679,000 19,571,000 -17,276,000 20,471,000 23,234,000 21,729,000 19,428,000 7,806,000 16,167,000 10,321,500 14,272,000 13,642,000  12,243,000 10,452,000 9,240,000                                 
      less: net income attributable to noncontrolling interest in subsidiary
                           774,000                                            
      net income attributable to brookline bancorp, inc.
                      26,663,000 18,679,000 19,571,000 -17,276,000 20,471,000 22,460,000 20,831,000 18,633,000 6,827,000 15,366,000 9,770,750 13,617,000 12,812,000  11,581,000 9,976,000 8,813,000 7,529,000 6,349,000 6,275,000 7,001,000 7,267,000 7,038,000 7,083,000 5,836,000 5,242,000 4,678,000 3,444,000                      
      gain on sales of investment securities
                             1,162,000                                          
      dividends declared per common share
                           100 100 100 90 90 90 90 90 90 85 85 85  85                               
      less net income attributable to noncontrolling interest in subsidiary
                            898,000 795,000 979,000 801,000 659,000 655,000 830,000 694,000 662,000 476,000 427,000 254,000 285,000 307,000 326,000 283,000 235,000 163,000 183,000 188,000 125,000 39,000                      
      gain on sales of loans and leases
                                496,500 588,000                                      
      weighted-average common shares outstanding during the period:
                                                                       
      basic
    89,104,605,000 89,103,510,000 88,983,248,000 89,033,463,000 88,904,692,000 88,894,577,000 88,230,681,000 88,795,270,000 88,665,135,000 86,563,641,000 77,079,278,000 76,779,038,000 77,091,013,000 77,617,227,000 77,974,851,000 78,000,261,000 78,150,364,000 78,143,752,000 78,951,892,000 78,948,139,000 78,849,282,000 79,481,462,000 79,669,922,000 80,315,050,000 80,184,977,000 77,879,593,000 74,459,508,000 76,452,539,000 70,261,954,000 70,299,722,000 70,186,921,000 70,049,829,000 69,989,909,000 69,886,576,000 69,762,784,000 69,677,656,000 69,664,619,000 58,640,775,000 58,629,265,000 58,611,488,000 58,586,274,000 58,574,230,000 58,370,569,000 58,522,547,000 58,491,808,000 57,919,412,000 57,571,596,000 57,488,499,000 58,541,627,000 59,749,897,000 60,534,234,000 60,363,461,000 60,309,532,000 60,054,059,000 60,108,206,000 60,086,614,000 59,944,866,000 57,373,970,000 57,247,354,000 57,076,261,000 56,644,208,000 56,599,521,000 57,468,369,000 57,583,175,000 26,306,216,000 26,272,049,000 26,778,953,000 
      diluted
    89,612,781,000 89,567,747,000 89,302,304,000 89,319,611,000 89,222,315,000 89,181,508,000 88,450,646,000 88,971,210,000 88,926,543,000 86,837,806,000 77,351,834,000 77,007,971,000 77,419,288,000 77,926,822,000 78,243,416,000 78,240,633,000 78,470,451,000 78,404,063,000 79,103,289,000 79,055,901,000 79,015,274,000 79,665,774,000 79,886,292,000 80,515,467,000 80,505,614,000 78,167,800,000 74,811,408,000 76,759,430,000 70,444,083,000 70,450,760,000 70,343,408,000 70,215,850,000 70,088,987,000 70,012,377,000 69,830,630,000 69,715,890,000 69,665,873,000 58,640,973,000 58,630,908,000 58,618,309,000 58,588,536,000 58,579,529,000 58,407,467,000 58,529,929,000 58,495,557,000 58,052,757,000 57,821,388,000 57,763,871,000 59,020,681,000 60,346,901,000 61,182,972,000 61,082,113,000 61,051,157,000 60,836,211,000 60,948,961,000 60,866,872,000 60,737,986,000 58,144,811,000  58,055,753,000 57,658,817,000 57,575,487,000 57,468,369,000 58,624,026,000 26,990,303,000 26,708,550,000 27,161,553,000 
      loss on sales of securities
                                     -13,000                                  
      (loss)/gain on sale/disposals of premises and equipment
                                    -2,000 -6,000                                  
      total non-interest income*
                                   4,867,000                                    
      income before benefit from income taxes*
                                   19,674,000                                    
      benefit from income taxes*
                                   7,115,000                                    
      net income before noncontrolling interest in subsidiary*
                                   12,559,000                                    
      net income attributable to brookline bancorp, inc.*
                                   11,865,000                                    
      earnings per common share:
                                                                       
      basic*
                                   170                                    
      diluted*
                                   170                                    
      (*) previously reported amounts prior to january 1, 2015 have been restated to reflect a retrospective change in accounting principle for investments in qualified affordable housing projects, in accordance with asu 2014-01. refer to note 8, "investments in qualified affordable projects".
                                                                       
      income from investments in affordable housing projects
                                    -543,000 -539,000                                  
      borrowed funds and subordinated debt
                                      3,109,000 3,617,000 3,840,000         6,819,000                      
      fees, charges and other income
                                      3,639,000 4,168,000 3,733,000 1,732,000 1,687,000 1,280,000 927,000 1,132,000 969,000 934,000 887,000 1,018,000                      
      income before provison for income taxes
                                      14,369,000                                 
      earnings per common share
                                                                       
      basic
    250 210 190 230 180 160 260 260 250 90 380 390 330 320 370 370 400 340 330 240 250 -220 260 280 260 240 90 200 180 190 180  170 140 130 110 90 110 120 120 120 120 100 90 80 60 60 50 70 80 80 80 90 100 90 90 90 80 80 80 80 120  90 190 210 180 
      diluted
    250 210 200 230 180 160 260 260 250 90 380 390 330 320 370 370 400 340 330 240 250 -220 260 280 260 240 90 200 180 190 180  170 140 130 110 90 110 120 120 120 120 100 90 80 60 60 50 70 80 80 80 90 90 90 90 90 80 80 80 80 120  90 190 210 180 
      gain on sales of securities
                                       797,000    80,000  834,000 1,045,000 594,000 346,000                       
      income before income taxes
                                       12,103,000 11,390,000 10,906,000 12,600,000 12,558,000 12,196,000 12,122,000 10,070,000 9,153,000 8,048,000 5,877,000       8,825,000 9,213,000 9,215,000 9,182,000 9,293,000 7,661,000 7,860,000 7,885,000 7,778,000 6,866,000 8,874,000 8,604,000 8,083,000 8,555,000 7,730,000 
      interest income:
                                                                       
      loans
                                         33,723,000 33,617,000 31,391,000 30,488,000 30,774,000 31,464,000 31,722,000 33,308,000 31,553,000 30,852,000 30,990,000 31,258,000 30,329,000 29,594,000 28,151,000 24,050,000 23,463,000 22,830,000 22,356,000 21,724,000 16,081,000 15,506,000 15,059,000        
      equity securities
                                         48,000 55,000 37,000 4,000 12,000    23,000                      
      total interest income
                                         35,286,000 35,452,000 33,209,000 32,451,000 32,775,000 33,660,000 34,322,000 36,222,000 34,854,000 35,378,000 35,887,000 36,843,000 36,097,000 35,567,000 33,149,000 29,124,000 28,359,000 27,284,000 26,324,000 25,130,000 18,113,000 17,893,000 17,011,000 16,609,000 15,345,000 17,286,000 18,632,000 17,686,000 17,351,000 19,059,000 
      income from investments in low income housing
                                                                       
      penalty from prepayment of borrowed funds
                                                                       
      loss on impairment of securities
                                                                       
      write-down of other real estate owned
                                         719,000                              
      earnings per common share attributable to brookline bancorp, inc.:
                                                                       
      basic
    250 210 190 230 180 160 260 260 250 90 380 390 330 320 370 370 400 340 330 240 250 -220 260 280 260 240 90 200 180 190 180  170 140 130 110 90 110 120 120 120 120 100 90 80 60 60 50 70 80 80 80 90 100 90 90 90 80 80 80 80 120  90 190 210 180 
      diluted
    250 210 200 230 180 160 260 260 250 90 380 390 330 320 370 370 400 340 330 240 250 -220 260 280 260 240 90 200 180 190 180  170 140 130 110 90 110 120 120 120 120 100 90 80 60 60 50 70 80 80 80 90 90 90 90 90 80 80 80 80 120  90 190 210 180 
      impairment losses on securities
                                                                       
      brokered deposits
                                              1,000  75,000 349,000 569,000 911,000 1,019,000 1,046,000 1,027,000 637,000                
      less non-credit loss on impairment of securities
                                              21,000   -53,000                      
      marketable equity securities
                                              21,000 22,000 21,000  55,000 67,000 15,000 7,000 28,000 30,000 33,000 40,000 78,000 76,000 74,000 65,000 69,000 78,000 90,000 96,000 111,000 109,000 138,000 132,000 153,000 
      subordinated debt
                                                   65,000 140,000 158,000 233,000 225,000 207,000 201,000 182,000 168,000 135,000           
      retail deposits
                                                8,180,000 8,580,000 10,163,000 11,512,000 11,476,000 11,138,000 10,718,000 8,385,000                
      impairment loss on securities
                                                 -779,000                      
      net impairment loss on securities
                                                 -726,000                      
      insurance
                                                 504,000                      
      fees and charges
                                                  1,107,000 943,000 926,000 1,272,000 1,019,000 961,000 573,000 725,000 798,000 1,206,000 851,000 496,000 549,000 1,121,000 572,000 714,000 546,000 378,000 448,000 368,000 508,000 
      loss on write-down of securities
                                                                       
      other income
                                                  16,000 15,000 1,000 9,000 30,000  69,000 92,750 130,000 107,000 174,000 142,000 211,000 140,000 173,000 181,000 68,000 121,000 158,000 161,000 123,000 
      income before income taxes and minority interest
                                                  6,155,000 4,488,000 7,026,000 7,999,000 8,103,000 8,294,000                
      net income before minority interest
                                                  3,738,000 2,740,000 4,315,000 4,896,000 4,985,000 4,996,000                
      minority interest in earnings of subsidiary
                                                  64,000 46,000 66,000 44,000 44,000 67,000                
      benefit from loan losses
                                                    1,503,000 1,107,000 1,249,000 859,000 748,000 840,000 32,000 957,000 654,000 635,000 711,000 330,000       275,000 
      net interest income after benefit from loan losses
                                                    16,494,000 16,944,000 16,884,000 16,830,000 15,880,000 16,073,000 16,917,000 16,173,000 16,400,000 12,026,000 12,176,000 11,845,000       10,587,000 
      gains on securities
                                                           259,000  806,000 381,000   181,000  302,000 312,000  871,000 
      amortization of identified intangibles
                                                    503,000 504,000  569,000                
      gains on sales of securities
                                                        558,000    594,000   581,000   328,000     
      merger/conversion
                                                          1,000 511,000 382,000           
      dividends on unvested restricted stock
                                                        169,000               
      dividend equivalent rights
                                                          339,000  363,000 359,000  375,000 361,000       
      amortization of core deposit intangible
                                                        526,000 592,000 593,000 593,000 593,000           
      swap agreement market valuation credit
                                                           6,000  50,000 88,000 39,000 60,000 18,000 18,000   53,000  
      recognition and retention plans
                                                         676,000 668,000 651,000  722,000 718,000 727,000        
      income tax expense:
                                                                       
      retroactive assessment related to reit
                                                                  5,515,000     
      total income tax expense
                                                             3,164,000 3,238,000 3,233,000 3,276,000 179,000 9,022,000     
      retroactive (credit) assessment related to reit
                                                                       
      weighted-average common shares outstanding during the period:
                                                                       
      basic
    89,104,605,000 89,103,510,000 88,983,248,000 89,033,463,000 88,904,692,000 88,894,577,000 88,230,681,000 88,795,270,000 88,665,135,000 86,563,641,000 77,079,278,000 76,779,038,000 77,091,013,000 77,617,227,000 77,974,851,000 78,000,261,000 78,150,364,000 78,143,752,000 78,951,892,000 78,948,139,000 78,849,282,000 79,481,462,000 79,669,922,000 80,315,050,000 80,184,977,000 77,879,593,000 74,459,508,000 76,452,539,000 70,261,954,000 70,299,722,000 70,186,921,000 70,049,829,000 69,989,909,000 69,886,576,000 69,762,784,000 69,677,656,000 69,664,619,000 58,640,775,000 58,629,265,000 58,611,488,000 58,586,274,000 58,574,230,000 58,370,569,000 58,522,547,000 58,491,808,000 57,919,412,000 57,571,596,000 57,488,499,000 58,541,627,000 59,749,897,000 60,534,234,000 60,363,461,000 60,309,532,000 60,054,059,000 60,108,206,000 60,086,614,000 59,944,866,000 57,373,970,000 57,247,354,000 57,076,261,000 56,644,208,000 56,599,521,000 57,468,369,000 57,583,175,000 26,306,216,000 26,272,049,000 26,778,953,000 
      diluted.
                                                              58,057,812,000         
      loans, excluding money market loan participations
                                                                14,403,000 13,914,000 13,255,000 14,215,000 14,392,000 14,439,000 15,901,000 
      money market loan participations
                                                                7,000 4,000 13,000 43,000 47,000 37,000 111,000 
      provision (credit) for loan losses
                                                                240,000 360,000 375,000     
      net interest income after provision (credit) for loan losses
                                                                11,901,000 10,352,000 12,048,000 12,061,000 10,929,000 10,771,000  
      income from pre-payment of fhlb advances
                                                                       
      swap agreement market valuation charge
                                                                       
      gain from termination of pension plan
                                                                       
      restructuring charge
                                                                       
      gains on sales and repayment of securities
                                                                     922,000  
      other real estate owned income
                                                                       
      swap contract market valuation adjustment
                                                                       
      recognition and retention plan
                                                                      42,000 
      internet bank start-up
                                                                       
    Balance Sheets:
    Quarterly
    Annual
      Unit: USD2025-06-30 2025-03-31 2024-12-31 2024-09-30 2024-06-30 2024-03-31 2023-12-31 2023-09-30 2023-06-30 2023-03-31 2022-12-31 2022-09-30 2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-06-30 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2016-12-31 2016-09-30 2016-03-31 2015-06-30 2014-09-30 2014-06-30 2013-03-31 2012-06-30 2012-03-31 2011-09-30 2011-06-30 2011-03-31 2010-09-30 2010-06-30 2009-12-31 2009-09-30 2009-06-30 2009-03-31 2008-06-30 2008-03-31 2007-09-30 2007-06-30 2007-03-31 2006-06-30 2006-03-31 2005-12-31 2005-09-30 2005-06-30 2005-03-31 2004-12-31 2004-09-30 2004-06-30 2004-03-31 2003-09-30 2003-06-30 2003-03-31 2002-09-30 2002-06-30 2002-03-31 2001-09-30 2001-06-30 
                                                                           
        assets
                                                                           
        cash and due from banks
      87,386,000 78,741,000 64,673,000 82,168,000 60,067,000 45,708,000 34,514,000 33,506,000 44,323,000 30,782,000 191,767,000 65,638,000 50,429,000 89,032,000 66,265,000 28,865,000 36,079,000 41,284,000 36,069,000 33,818,000 38,522,000 86,996,000 46,532,000 30,762,000 32,724,000 34,713,000 25,622,000 35,392,000 36,055,000 32,196,000 31,127,000 43,363,000 37,237,000 58,962,000 39,330,000 118,411,000 88,884,000 22,919,000 23,412,000 23,241,000 18,870,000 20,592,000 17,635,000 16,048,000 18,363,000 16,696,000 17,139,000 16,976,000 15,665,000 16,679,000 16,314,000 17,528,000 15,307,000 15,507,000 16,004,000 17,558,000 10,491,000 8,937,000 8,262,000 9,639,000 14,886,000 12,547,000 12,870,000 11,651,000 13,055,000 16,802,000 13,431,000 12,919,000 13,144,000 
        short-term investments
      419,362,000 278,805,000 478,997,000 325,721,000 283,017,000 256,178,000 98,513,000 127,495,000 180,109,000 455,538,000 191,192,000 46,873,000 39,900,000 204,239,000 261,472,000 210,279,000 284,370,000 89,643,000 398,848,000 283,515,000 216,394,000 253,772,000 46,264,000 23,114,000 22,754,000 49,743,000 35,383,000 27,971,000 31,602,000 32,351,000 42,795,000 48,513,000 50,901,000 20,771,000 52,766,000 98,677,000 44,382,000 82,962,000 93,861,000 73,165,000 49,349,000 67,622,000 48,886,000 93,842,000 98,364,000 75,571,000 86,737,000 78,925,000 130,254,000 134,853,000 140,320,000 107,950,000 108,954,000 102,888,000 133,707,000 163,762,000 133,549,000 127,928,000 99,556,000 118,748,000 140,402,000 121,610,000 90,841,000 148,897,000 353,800,000 404,518,000 63,229,000 26,963,000 28,972,000 
        total cash and cash equivalents
      506,748,000 357,546,000 543,670,000 407,889,000 343,084,000 301,886,000 133,027,000 161,001,000 224,432,000 486,320,000 382,959,000 112,511,000 90,329,000 293,271,000 327,737,000 239,144,000 320,449,000 130,927,000 434,917,000 317,333,000 254,916,000 340,768,000 92,796,000 53,876,000 55,478,000 84,456,000 61,005,000 63,363,000 67,657,000 64,547,000 73,922,000 91,876,000 88,138,000 79,733,000 92,096,000 217,088,000 133,266,000                                 
        investment securities available-for-sale
      866,684,000 882,353,000 895,034,000 855,391,000 856,439,000 865,798,000 916,601,000 880,412,000 910,210,000 1,067,032,000 656,766,000 675,692,000 717,818,000 730,562,000 720,866,000 732,020,000 694,151,000 729,901,000 745,822,000 783,867,000 854,505,000 761,539,000 482,497,000 534,788,000 558,602,000 558,357,000 540,124,000 522,910,000 523,634,000 524,295,000 536,182,000 530,476,000 527,516,000 528,586,000 486,625,000 384,533,000                                  
        total investment securities
      866,684,000 882,353,000 895,034,000 855,391,000 856,439,000 865,798,000 916,601,000 880,412,000 910,210,000 1,067,032,000 656,766,000  717,818,000 730,562,000 720,866,000 732,020,000 694,151,000 730,419,000 746,348,000 784,392,000 856,497,000 764,097,000 590,767,000 654,641,000 675,272,000 675,709,000 649,854,000 630,648,000 610,754,000 601,389,000 619,591,000 590,987,000 528,016,000 529,086,000 487,125,000                                   
        allowance for investment security credit losses
      -97,000 -94,000                                                                    
        net investment securities
      866,587,000 882,259,000 894,952,000 855,205,000 856,080,000 865,400,000 916,160,000 879,895,000 909,777,000    717,760,000 730,558,000                                                        
        loans and leases:
                                                                           
        commercial real estate loans
      5,485,546,000 5,580,982,000 5,716,114,000 5,779,290,000 5,782,111,000 5,755,239,000 5,764,529,000 5,669,768,000 5,670,771,000 5,610,414,000 4,404,148,000 4,269,512,000 4,225,754,000 4,235,325,000 4,103,040,000 3,909,011,000 3,815,581,000 3,790,341,000 3,823,826,000 3,835,372,000 3,837,703,000 3,762,158,000 3,493,554,000 3,281,045,000 3,264,166,000 3,240,258,000 3,075,777,000 3,029,009,000 2,918,567,000 2,883,428,000 2,766,398,000 2,513,358,000 2,402,723,000 2,314,585,000 2,001,061,000                                   
        commercial loans and leases
      2,520,347,000 2,512,912,000 2,506,664,000 2,453,038,000 2,443,530,000 2,416,904,000 2,399,668,000 2,241,375,000 2,193,027,000 2,147,149,000 2,016,499,000 1,933,645,000 1,860,182,000 1,800,383,000 1,887,136,000 1,869,686,000 2,038,851,000 2,324,202,000 2,274,899,000 2,354,613,000 2,361,463,000 1,826,866,000 1,826,336,000 1,777,984,000 1,736,144,000 1,707,002,000 1,624,111,000 1,585,296,000 1,495,408,000 1,470,866,000 1,398,639,000 1,282,180,000 1,121,853,000 1,076,953,000                                    
        consumer loans
      1,576,481,000 1,548,828,000 1,556,510,000 1,522,908,000 1,495,496,000 1,482,943,000 1,477,392,000 1,469,639,000 1,477,001,000 1,489,402,000 1,223,741,000 1,218,147,000 1,205,976,000 1,187,422,000 1,164,281,000 1,152,997,000 1,165,843,000 1,153,009,000 1,170,828,000 1,206,373,000 1,208,531,000 1,233,503,000 1,185,439,000 1,168,678,000 1,170,964,000 1,167,201,000 1,030,791,000 1,025,135,000 978,748,000 970,399,000 954,188,000 914,666,000 858,189,000 836,061,000 770,445,000                                   
        total loans and leases
      9,582,374,000 9,642,722,000 9,779,288,000 9,755,236,000 9,721,137,000 9,655,086,000 9,641,589,000 9,380,782,000 9,340,799,000 9,246,965,000 7,644,388,000 7,421,304,000 7,291,912,000 7,223,130,000 7,154,457,000 6,931,694,000 7,020,275,000 7,267,552,000 7,269,553,000 7,396,358,000 7,407,697,000 6,822,527,000 6,505,329,000 6,227,707,000 6,171,274,000 6,114,461,000 5,730,679,000 5,639,440,000 5,398,864,000 5,332,300,000 5,130,445,000 4,729,581,000 4,736,028,000 4,603,913,000 4,173,985,000                                   
        allowance for loan and lease losses
      -126,725,000 -124,145,000 -125,083,000 -127,316,000 -121,750,000 -120,124,000 -117,522,000 -119,081,000 -125,817,000 -120,865,000 -98,482,000 -94,169,000 -93,188,000 -95,463,000 -99,084,000 -102,515,000 -106,474,000 -109,837,000 -114,379,000 -119,971,000 -119,553,000 -113,181,000 -58,635,000 -59,997,000 -57,981,000 -58,714,000 -58,592,000 -65,413,000 -53,666,000 -58,892,000 -58,606,000 -56,398,000 -52,822,000 -51,686,000                                    
        net loans and leases
      9,455,649,000 9,518,577,000 9,654,205,000 9,627,920,000 9,599,387,000 9,534,962,000 9,524,067,000 9,261,701,000 9,214,982,000 9,126,100,000 7,545,906,000 7,327,135,000 7,198,724,000 7,127,667,000 7,055,373,000 6,829,179,000 6,913,801,000 7,157,715,000 7,155,174,000 7,276,387,000 7,288,144,000 6,709,346,000 6,446,694,000 6,167,710,000 6,113,293,000 6,055,747,000 5,672,087,000 5,574,027,000 5,345,198,000 5,273,408,000 5,071,839,000 4,673,183,000 4,683,206,000 4,552,227,000 4,131,453,000 3,975,698,000 3,901,090,000                                 
        restricted equity securities
      66,481,000 67,537,000 83,155,000 82,675,000 78,963,000 74,709,000 77,595,000 65,460,000 71,421,000 86,230,000 71,307,000 44,760,000 35,406,000 29,066,000 28,981,000 28,098,000 31,627,000 40,400,000 49,786,000 61,715,000 71,638,000 68,472,000 55,270,000 63,963,000 68,343,000 66,164,000 59,369,000 62,135,000 64,511,000 65,683,000 65,438,000 75,553,000 74,804,000 71,446,000 66,553,000 61,291,000 53,554,000 39,283,000 39,794,000 39,612,000 36,335,000 36,335,000 36,335,000 36,335,000 36,335,000 36,335,000 32,638,000 28,365,000 26,563,000 26,563,000 26,563,000 28,567,000 24,608,000 23,081,000 23,081,000 23,081,000 22,557,000 17,444,000 16,554,000 15,125,000 14,239,000 9,423,000 9,423,000 9,423,000 9,423,000 9,423,000 9,423,000 9,187,000 8,506,000 
        premises and equipment
      83,963,000 84,439,000 86,781,000 86,925,000 88,378,000 89,707,000 89,853,000 90,476,000 90,685,000 87,799,000 71,391,000 69,912,000 69,557,000 69,365,000 70,359,000 70,811,000 71,240,000 72,524,000 71,568,000 72,441,000 73,127,000 73,786,000 75,373,000 77,886,000 79,194,000 80,268,000 80,283,000 81,159,000 76,176,000 75,462,000 77,128,000 77,892,000 81,479,000 82,166,000 74,223,000 56,248,000 48,908,000                                 
        right-of-use asset operating leases
      42,415,000 44,144,000 43,527,000 41,934,000 35,691,000 33,133,000 30,863,000 31,619,000 31,774,000 30,067,000 19,484,000 18,614,000 18,226,000 19,571,000 20,508,000 21,879,000 22,682,000 23,180,000 24,143,000 23,492,000 24,343,000 24,789,000 25,928,000                                               
        deferred tax asset
      52,325,000 52,176,000 56,620,000 50,827,000 60,032,000 60,484,000 56,952,000 74,491,000 77,704,000 75,028,000 52,237,000 56,894,000 50,736,000 46,886,000 38,987,000 39,643,000 41,324,000 42,857,000 40,129,000 42,269,000 42,683,000 38,141,000 25,629,000 22,249,000 20,826,000 19,198,000 15,061,000 28,093,000 25,247,000 22,894,000 24,181,000 28,466,000 29,168,000 27,799,000 29,123,000 25,656,000 24,647,000 11,840,000 12,541,000 13,552,000 9,012,000 9,325,000 10,178,000 10,249,000 10,686,000 12,995,000 12,247,000 10,133,000 10,936,000 11,098,000 10,362,000  11,246,000 11,347,000 9,486,000 8,623,000 8,434,000 9,980,000 9,725,000 9,116,000 8,109,000 6,868,000 7,212,000 9,516,000 3,071,000 2,292,000 4,141,000 4,984,000 5,475,000 
        goodwill
      241,222,000 241,222,000 241,222,000 241,222,000 241,222,000 241,222,000 241,222,000 241,222,000 241,222,000 241,222,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,427,000 160,896,000 137,890,000 137,890,000 137,890,000 137,890,000 137,890,000 137,890,000 137,890,000 137,890,000 137,890,000 137,890,000 138,914,000 46,203,000 45,966,000 46,854,000 43,241,000 43,241,000 43,241,000 43,241,000 43,241,000 43,241,000 43,241,000 43,241,000 42,545,000 42,545,000 42,545,000 42,316,000 35,615,000 35,615,000 35,615,000 35,597,000 36,605,000             
        identified intangible assets, net of accumulated amortization of 17,265 and 16,526, respectively
      14,600,000                                                                     
        oreo and repossessed assets
      1,288,000 917,000 1,103,000 1,579,000 1,974,000                                                                 
        other assets
      237,467,000 255,022,000 282,630,000 261,383,000 309,651,000 310,195,000 286,616,000 348,219,000 315,353,000 292,099,000 223,170,000 227,270,000 170,536,000 153,793,000 176,390,000 188,363,000 203,199,000 192,058,000 250,265,000 256,859,000 292,662,000 275,640,000 155,291,000 108,350,000 100,331,000 93,260,000 91,609,000 95,035,000 88,086,000 108,024,000 97,288,000  77,966,000 76,804,000 69,483,000 80,088,000 80,205,000 16,630,000 15,670,000 12,715,000 11,272,000 10,974,000 10,420,000 4,377,000 4,728,000 4,469,000 4,497,000 5,045,000 4,608,000 4,137,000 4,500,000 4,042,000 3,550,000 3,111,000 2,972,000 1,968,000 2,172,000 1,945,000 1,572,000 1,131,000 1,135,000 593,000 417,000 496,000 369,000 613,000 515,000 566,000 2,509,000 
        total assets
      11,568,745,000 11,519,869,000 11,905,326,000 11,676,721,000 11,635,292,000 11,542,731,000 11,382,256,000 11,180,555,000 11,206,078,000 11,522,485,000 9,185,836,000 8,695,708,000 8,514,230,000 8,633,736,000 8,602,622,000 8,312,649,000 8,461,964,000 8,559,810,000 8,942,424,000 9,000,192,000 9,069,667,000 8,461,591,000 7,636,980,000 7,320,596,000 7,285,710,000 7,248,114,000 6,780,249,000 6,686,284,000 6,438,129,000 6,380,312,000 6,181,030,000  5,717,965,000 5,587,486,000 5,110,378,000 4,972,381,000 4,877,124,000 3,157,498,000 3,114,582,000 3,057,772,000 2,660,396,000 2,659,418,000 2,615,884,000 2,638,914,000 2,641,113,000 2,623,913,000 2,494,616,000 2,454,340,000 2,391,906,000 2,371,609,000 2,351,494,000 2,381,365,000 2,243,080,000 2,214,704,000 2,207,088,000 2,216,146,000 2,184,994,000 1,694,499,000 1,643,274,000 1,610,218,000 1,591,208,000 1,458,459,000 1,414,208,000 1,424,046,000 1,451,318,000 1,515,442,000 1,129,794,000 1,096,691,000 1,079,058,000 
        liabilities and stockholders' equity
                                                                           
        deposits:
                                                                           
        demand checking accounts
      1,726,933,000 1,664,629,000 1,692,394,000 1,681,858,000 1,638,378,000 1,629,371,000 1,678,406,000 1,745,137,000 1,843,516,000 1,899,370,000 1,802,518,000 1,848,562,000 1,845,365,000 1,903,331,000 1,888,462,000 1,816,116,000 1,926,713,000 1,724,170,000 1,592,205,000 1,550,267,000 1,603,037,000 1,175,329,000 1,042,854,000 1,017,234,000 1,002,954,000 987,153,000 942,583,000 905,472,000 900,474,000 889,278,000 793,195,000 783,331,000 705,604,000 716,883,000 623,315,000 546,036,000 529,945,000                                 
        interest-bearing deposits
      7,234,269,000 7,246,823,000  7,050,413,000 7,098,658,000 7,089,282,000  6,820,876,000 6,673,497,000 6,557,092,000  4,887,043,000 5,049,092,000 5,191,047,000  5,056,894,000 4,967,988,000 5,142,616,000  5,242,256,000 4,837,196,000 4,714,609,000                                                
        total deposits
      8,961,202,000 8,911,452,000 8,901,644,000 8,732,271,000 8,737,036,000 8,718,653,000 8,548,125,000 8,566,013,000 8,517,013,000 8,456,462,000 6,522,146,000 6,735,605,000 6,894,457,000 7,094,378,000 7,049,906,000 6,873,010,000 6,894,701,000 6,866,786,000 6,910,696,000 6,792,523,000 6,440,233,000 5,889,938,000 5,622,493,000 5,233,611,000 5,198,280,000 5,191,520,000 4,871,343,000 4,805,683,000 4,611,076,000 4,564,906,000 4,393,456,000 4,129,408,000 3,889,204,000 3,861,147,000 3,626,033,000 3,521,206,000 3,459,333,000                                 
        borrowed funds:
                                                                           
        advances from the fhlb
      934,669,000 957,848,000 1,355,926,000 1,345,003,000 1,265,079,000                                698,671,000                                 
        subordinated debentures and notes
      84,397,000 84,362,000 84,328,000 84,293,000 84,258,000 84,223,000 84,188,000 84,152,000 84,116,000 84,080,000 84,044,000 84,008,000 83,970,000 83,934,000 83,897,000 83,859,000 83,821,000 83,783,000 83,746,000 83,707,000 83,668,000 83,630,000 83,512,000 83,392,000 83,352,000 83,311,000 83,271,000 83,229,000 83,105,000 83,043,000 82,978,000 82,850,000 82,763,000                                     
        other borrowed funds
      135,985,000 113,617,000 79,592,000 68,251,000 80,125,000 127,505,000 69,256,000 151,612,000 98,773,000 87,565,000 110,785,000 116,865,000 86,263,000 107,727,000 125,517,000 69,703,000 75,039,000 83,574,000 87,652,000 80,169,000 55,431,000 70,743,000 55,693,000 40,048,000 36,480,000 33,585,000 47,639,000 30,087,000 50,207,000 38,639,000 39,378,000 31,346,000 22,891,000 35,360,000 60,772,000 60,707,000  6,947,000 4,789,000                               
        total borrowed funds
      1,155,051,000 1,155,827,000 1,519,846,000 1,497,547,000 1,429,462,000 1,361,881,000 1,376,670,000 1,135,068,000 1,226,270,000 1,630,102,000 1,432,652,000 758,768,000 478,200,000 392,897,000 357,321,000 267,539,000 363,014,000 546,003,000 820,247,000 1,005,045,000 1,406,669,000 1,291,804,000 930,764,000 1,082,886,000 1,110,923,000 1,099,429,000 1,020,819,000 985,895,000 1,044,086,000 1,022,653,000 1,028,309,000 937,648,000 1,132,865,000 1,041,004,000 820,447,000 794,101,000 758,536,000                                 
        operating lease liabilities
      43,528,000 45,330,000 44,785,000 43,266,000 37,102,000 34,235,000 31,998,000 32,807,000 33,021,000 31,373,000 19,484,000 18,614,000 18,226,000 19,571,000 20,508,000 21,879,000 22,682,000 23,180,000 24,143,000 23,492,000 24,343,000 24,789,000 25,928,000                                               
        mortgagors' escrow accounts
      15,289,000 15,264,000 15,875,000 14,456,000 17,117,000 16,245,000 17,239,000 12,578,000 17,207,000 17,080,000 5,607,000 5,785,000 5,771,000 5,780,000 6,296,000 6,455,000 6,231,000 6,483,000 5,901,000 6,429,000 6,467,000 7,441,000 6,823,000 8,227,000 8,122,000 8,395,000 7,686,000 8,151,000 7,645,000                                       4,617,000 4,211,000 
        reserve for unfunded credits
      4,586,000 5,296,000 5,981,000 6,859,000 11,400,000 15,807,000 19,767,000 21,497,000 22,789,000 23,112,000 20,602,000 19,555,000 17,511,000 16,305,000  12,736,000 13,142,000 13,705,000    17,222,000                                                
        accrued expenses and other liabilities
      134,918,000 146,518,000 195,256,000 151,960,000 204,695,000 201,679,000 189,813,000 254,721,000 227,470,000 199,290,000 193,220,000 193,763,000 131,569,000 122,870,000 173,249,000 152,578,000 189,942,000 158,254,000 239,659,000 237,145,000 265,542,000 317,829,000 132,504,000 96,047,000 82,017,000 74,024,000 67,818,000 74,019,000 72,573,000 81,670,000 64,566,000 49,792,000 50,430,000 45,411,000 38,825,000 47,328,000 50,883,000 21,042,000 18,742,000 21,935,000 18,112,000 16,949,000 16,955,000 18,208,000 18,165,000 19,895,000 20,122,000 20,237,000 21,997,000 21,683,000 21,139,000 18,778,000 13,065,000 14,215,000 12,118,000 12,351,000 13,402,000 10,893,000 12,457,000 10,173,000 11,146,000 10,007,000 8,512,000 8,534,000 7,138,000 7,025,000 6,627,000 8,992,000 10,475,000 
        total liabilities
      10,314,574,000 10,279,687,000 10,683,387,000 10,446,359,000 10,436,812,000 10,348,500,000 10,183,612,000 10,022,684,000 10,043,770,000 10,357,419,000 8,193,711,000 7,732,090,000 7,545,734,000 7,651,801,000 7,607,280,000 7,334,197,000 7,489,712,000 7,614,411,000 8,000,646,000 8,064,634,000 8,143,254,000 7,549,023,000 6,718,512,000 6,420,771,000 6,399,342,000 6,373,368,000 5,967,666,000 5,873,748,000 5,735,380,000 5,677,395,000 5,494,236,000 5,124,342,000 5,081,256,000 4,955,921,000 4,493,128,000 4,369,577,000 4,275,908,000 2,652,511,000 2,610,866,000 2,557,402,000 2,162,842,000 2,164,940,000 2,126,461,000 2,149,480,000 2,153,738,000  1,987,559,000 1,944,957,000 1,859,102,000 1,823,331,000 1,782,481,000 1,788,816,000 1,652,540,000 1,612,254,000 1,605,582,000 1,603,024,000 1,572,686,000 1,109,486,000 1,058,231,000 1,013,976,000 995,055,000 854,139,000 799,365,000 810,535,000 813,772,000 1,218,995,000 840,159,000 808,675,000 792,680,000 
        commitments and contingencies
                                                                           
        stockholders' equity:
                                                                           
        brookline bancorp, inc. stockholders' equity:
                                                                           
        common stock, 0.01 par value...
      970,000 970,000 970,000 970,000 970,000 970,000 970,000 970,000 970,000 970,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 852,000 817,000 817,000 757,000 757,000 757,000 757,000 757,000 757,000 754,000 754,000 754,000 644,000 644,000 644,000 644,000 644,000 644,000 644,000 644,000 643,000 637,000 636,000 633,000 631,000 631,000 630,000 630,000 630,000 630,000 630,000 630,000 605,000 605,000 604,000 603,000 590,000 589,000 589,000 587,000 297,000 297,000   
        additional paid-in capital
      904,697,000 903,696,000 902,584,000 901,562,000 904,775,000 903,726,000 902,659,000 901,376,000 905,084,000 904,174,000 736,074,000 735,119,000 738,544,000 737,658,000 736,826,000 735,990,000 738,557,000 737,882,000 737,178,000 736,294,000 738,155,000 737,422,000 737,584,000 753,941,000 756,254,000 755,843,000 699,976,000 697,888,000 616,734,000 616,142,000 617,477,000 618,044,000 616,997,000 617,709,000 618,711,000 618,184,000 618,031,000 525,012,000 524,841,000 524,671,000 524,336,000 524,191,000 523,736,000 523,298,000 523,140,000 522,114,000 517,268,000 515,826,000 511,758,000 510,511,000 509,428,000 506,293,000 505,267,000 512,338,000 512,163,000 511,918,000 511,768,000 471,799,000 471,580,000 471,100,000 470,248,000 451,512,000 451,151,000 450,893,000 448,734,000 141,412,000 141,276,000 140,944,000 140,356,000 
        retained earnings
      475,781,000 465,898,000 458,943,000 453,555,000 445,560,000 441,285,000 438,722,000 427,937,000 417,328,000 407,528,000 412,019,000                                                         173,549,000 170,496,000 
        accumulated other comprehensive income
      -39,378,000 -42,498,000 -52,882,000 -38,081,000 -61,693,000 -60,841,000 -52,798,000 -81,541,000 -66,156,000 -52,688,000 -61,947,000 -70,227,000 -44,977,000 -29,322,000 -110,000 2,615,000 6,089,000 2,082,000  18,782,000 19,538,000 16,947,000             2,233,000 1,969,000 2,457,000 2,540,000 3,254,000 2,007,000 3,828,000 3,257,000 2,201,000 3,802,000 2,378,000 1,806,000  1,974,000 7,000         560,000 717,000 1,003,000 2,411,000 3,424,000 2,673,000 3,279,000 8,949,000 9,968,000 6,798,000 6,314,000 6,684,000 
        treasury stock
      -87,899,000 -87,884,000 -87,676,000 -87,644,000 -91,132,000 -90,909,000 -90,909,000 -90,871,000 -94,918,000 -94,918,000 -94,873,000 -94,866,000 -98,525,000 -84,718,000 -84,718,000 -84,684,000 -77,493,000 -77,463,000 -77,343,000 -67,376,000 -69,572,000 -69,617,000 -59,199,000 -48,334,000 -51,454,000 -51,454,000 -51,454,000 -51,452,000 -53,837,000 -54,151,000 -56,208,000 -58,372,000 -58,228,000 -59,487,000            -62,107,000                        
        total stockholders' equity
      1,254,171,000 1,240,182,000 1,221,939,000 1,230,362,000 1,198,480,000 1,194,231,000 1,198,644,000 1,157,871,000 1,162,308,000 1,165,066,000 992,125,000 963,618,000 968,496,000 981,935,000 995,342,000 978,452,000 972,252,000 945,399,000 941,778,000 935,558,000 926,413,000 912,568,000 918,468,000 899,825,000 886,368,000 874,746,000 812,583,000 812,536,000 702,749,000 702,917,000 686,794,000  636,709,000 631,565,000                                    
        total liabilities and stockholders' equity
      11,568,745,000 11,519,869,000 11,905,326,000 11,676,721,000 11,635,292,000 11,542,731,000 11,382,256,000 11,180,555,000 11,206,078,000 11,522,485,000 9,185,836,000 8,695,708,000 8,514,230,000 8,633,736,000 8,602,622,000 8,312,649,000 8,461,964,000 8,559,810,000 8,942,424,000 9,000,192,000 9,069,667,000 8,461,591,000 7,636,980,000 7,320,596,000 7,285,710,000 7,248,114,000 6,780,249,000 6,686,284,000 6,438,129,000 6,380,312,000 6,181,030,000  5,717,965,000 5,587,486,000                                    
        identified intangible assets, net of accumulated amortization of 17,956 and 16,526, respectively
       16,030,000                                                                    
        allowance for investment security losses
        -82,000 -186,000 -359,000 -398,000 -441,000 -517,000 -433,000    -58,000 -4,000                                                        
        identified intangible assets, net of accumulated amortization of 16,526 and 47,963, respectively
        17,461,000                                                                   
        non-interest-bearing deposits:
                                                                           
        interest-bearing deposits:
                                                                           
        now accounts
        617,246,000    661,863,000    544,118,000    604,097,000    513,948,000    340,082,000 322,587,000 346,936,000 342,374,000 350,568,000 318,284,000 323,160,000 298,629,000 286,920,000 247,172,000 220,766,000 209,682,000 194,313,000 185,234,000 181,299,000                                 
        savings accounts
        1,721,247,000    1,669,018,000    762,271,000    915,804,000    701,659,000    585,322,000 612,210,000 603,079,000 637,920,000 646,359,000 665,558,000 613,061,000 591,156,000 555,843,000 532,184,000 532,790,000 518,343,000 509,967,000 503,507,000 511,736,000                                 
        money market accounts
        2,116,360,000    2,082,810,000    2,174,952,000    2,358,306,000    2,018,977,000    1,669,782,000 1,623,220,000 1,704,652,000 1,862,351,000 1,724,363,000 1,749,040,000 1,733,359,000 1,679,797,000 1,649,348,000 1,523,798,000 1,522,612,000 1,516,023,000 1,303,231,000                                   
        certificate of deposit accounts
        1,885,444,000    1,574,855,000    928,143,000    1,117,695,000    1,389,998,000    1,984,453,000 1,658,360,000 1,540,659,000 1,361,722,000 1,207,470,000 1,167,329,000 1,041,022,000 1,106,046,000 1,108,150,000 1,042,923,000 907,432,000 900,216,000 995,207,000 1,049,462,000 1,061,548,000                                 
        brokered deposit accounts
        868,953,000    881,173,000    310,144,000    165,542,000    693,909,000                                                   
        total interest-bearing deposits
        7,209,250,000    6,869,719,000    4,719,628,000    5,161,444,000    5,318,491,000    4,579,639,000 4,216,377,000 4,195,326,000 4,204,367,000 3,928,760,000 3,900,211,000 3,710,602,000 3,675,628,000 3,600,261,000 3,346,077,000 3,183,600,000 3,144,264,000 3,002,718,000                                   
        identified intangible assets, net of accumulated amortization of 14,825 and 47,963, respectively
         19,162,000                                                                  
        identified intangible assets, net of accumulated amortization of 13,157 and 47,963, respectively
          20,830,000                                                                 
        loans held-for-sale
           6,717,000                 1,575,000 937,000 1,034,000 756,000 2,628,000 2,973,000 13,078,000      839,000                                   
        identified intangible assets, net of accumulated amortization of 11,488 and 47,963, respectively
           22,499,000                                                                
        other real estate owned ("oreo") and repossessed assets
           1,817,000 1,694,000 299,000 602,000 508,000 408,000 591,000 507,000 990,000 718,000 601,000 372,000 6,383,000 6,515,000 1,413,000 1,454,000 2,038,000 1,966,000 3,934,000 4,352,000 3,963,000 4,419,000 4,398,000 1,399,000 1,152,000 565,000 2,412,000                                      
        advances from the federal home loan bank
           1,150,153,000                                                                
        identified intangible assets, net of accumulated amortization of 47,963 and 40,123, respectively
            24,207,000                                                               
        advances from the federal home loan bank ("fhlb") of boston and new york
            1,223,226,000 899,304,000                                                              
        identified intangible assets, net of accumulated amortization of 45,998 and 40,123, respectively
             26,172,000                                                              
        identified intangible assets, net of accumulated amortization of 44,043 and 40,123, respectively
              28,126,000                                                             
        advances from the federal home loan bank of boston and new york
              1,043,381,000 1,458,457,000                                                            
        identified intangible assets, net of accumulated amortization of 42,089 and 40,123, respectively
               30,080,000                                                            
        identified intangible assets, net of accumulated amortization of 40,123 and 39,628, respectively
                1,781,000                                                           
        advances from the federal home loan bank of boston
                1,237,823,000 557,895,000 307,967,000 201,236,000 147,907,000 113,977,000 204,154,000 378,646,000 648,849,000 841,169,000 1,267,570,000 1,137,431,000 791,559,000 959,446,000 991,091,000 982,533,000 889,909,000 872,579,000 910,774,000 900,971,000 905,953,000 823,452,000                                      
        unallocated common stock held by esop; 0 shares and 24,660 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 40,002 and 39,628, respectively
                 1,902,000                                                          
        retained earnings, partially restricted
                 392,779,000 372,677,000 357,576,000 342,639,000 323,862,000 304,466,000 282,301,000 264,892,000 247,336,000 237,808,000 227,359,000 238,625,000 200,151,000 185,734,000 172,934,000 161,217,000 160,225,000 136,671,000 129,740,000 116,151,000  78,980,000 73,373,000 56,211,000 42,006,000 40,398,000 37,926,000 36,633,000 34,618,000 30,937,000 28,876,000 25,420,000 24,519,000 24,299,000 24,634,000 53,433,000 54,701,000 70,109,000 83,133,000 83,388,000 108,645,000 108,845,000 121,042,000 120,620,000 132,497,000 132,196,000 144,081,000 144,977,000 157,174,000 157,439,000 170,824,000 182,584,000 180,720,000 184,829,000 184,275,000 180,896,000   
        unallocated common stock held by employee stock ownership plan ("esop"); 4,833 shares and 24,660 shares, respectively
                 -39,000                                                          
        identified intangible assets, net of accumulated amortization of 39,882 and 39,628, respectively
                  2,022,000                                                         
        unallocated common stock held by employee stock ownership plan ("esop"); 11,442 shares and 24,660 shares, respectively
                  -75,000                                                         
        identified intangible assets, net of accumulated amortization of 39,762 and 39,628, respectively
                   2,142,000                                                        
        unallocated common stock held by employee stock ownership plan ("esop"); 18,051 shares and 24,660 shares, respectively
                   -111,000                                                        
        equity securities held-for-trading
                       518,000 526,000 525,000 1,992,000 2,558,000 4,698,000                                               
        identified intangible assets, net of accumulated amortization of 39,628 and 38,752, respectively
                    2,276,000                                                       
        unallocated common stock held by esop; 24,660 shares and 51,114 shares, respectively
                    -147,000                                                       
        identified intangible assets, net of accumulated amortization of 39,420 and 38,752, respectively
                     2,484,000                                                      
        unallocated common stock held by employee stock ownership plan ("esop"); 31,278 shares and 51,114 shares, respectively
                     -183,000                                                      
        identified intangible assets, net of accumulated amortization of 39,212 and 38,752, respectively
                      2,692,000                                                     
        unallocated common stock held by employee stock ownership plan ("esop"); 37,890 shares and 51,114 shares, respectively
                      -219,000                                                     
        identified intangible assets, net of accumulated amortization of 38,984 and 38,752, respectively
                       2,920,000                                                    
        unallocated common stock held by employee stock ownership plan ("esop"); 44,502 shares and 51,114 shares, respectively
                       -255,000                                                    
        investment securities held-to-maturity
                            103,572,000 115,684,000 116,670,000 117,352,000 109,730,000 107,738,000 87,120,000 77,094,000 83,409,000 60,511,000 500,000 500,000 500,000                                   
        identified intangible assets, net of accumulated amortization of 38,752 and 37,481, respectively
                        3,152,000                                                   
        accumulated other comprehensive loss
                        16,490,000    1,141,000 -15,599,000 -13,415,000 -11,666,000 -5,950,000 -1,893,000 -3,818,000   -1,775,000 -4,681,000 -3,209,000                                    
        unallocated common stock held by esop; 51,114 shares and 79,548 shares, respectively
                        -291,000                                                   
        identified intangible assets, net of accumulated amortization of 38,440 and 37,481, respectively
                         3,464,000                                                  
        unallocated common stock held by employee stock ownership plan ("esop"); 58,227 shares and 79,548 shares, respectively
                         -330,000                                                  
        identified intangible assets, net of accumulated amortization of 38,128 and 37,481, respectively
                          3,776,000                                                 
        unallocated common stock held by employee stock ownership plan ("esop"); 65,334 shares and 79,548 shares, respectively
                          -368,000                                                 
        identified intangible assets, net of accumulated amortization of 37,817 and 37,481, respectively
                           4,087,000                                                
        unallocated common stock held by employee stock ownership plan ("esop"); 72,441 shares and 79,548 shares, respectively
                           -395,000                                                
        identified intangible assets, net of accumulated amortization of 37,999 and 35,818, respectively
                            5,264,000                                               
        unallocated common stock held by employee stock ownership plan ("esop"); 98,208 shares and 109,950 shares, respectively
                            -535,000                                               
        total brookline bancorp, inc. stockholders' equity
                            918,468,000 890,368,000 877,283,000 865,777,000 803,830,000 804,762,000 695,544,000                                         
        noncontrolling interest in subsidiary
                             9,457,000 9,085,000 8,969,000 8,753,000 7,774,000 7,205,000 6,546,000 6,377,000 5,076,000 4,309,000 3,902,000 3,211,000 3,939,000 3,685,000 3,097,000 2,639,000 2,788,000 2,297,000 2,062,000 2,106,000 1,923,000 1,734,000 1,870,000                        
        equity securities held for trading
                             4,169,000                                              
        identified intangible assets, net of accumulated amortization of 35,281 and 33,738, respectively
                             6,623,000                                              
        unallocated common stock held by employee stock ownership plan ("esop"); 118,050 shares and 142,332 shares, respectively
                             -643,000                                              
        identified intangible assets, net of accumulated amortization of 34,744 and 33,738, respectively
                              7,160,000                                             
        unallocated common stock held by employee stock ownership plan ("esop"); 126,144 shares and 142,332 shares, respectively
                              -688,000                                             
        identified intangible assets, net of accumulated amortization of 34,205 and 33,738, respectively
                               7,697,000                                            
        unallocated common stock held by employee stock ownership plan ("esop"); 134,238 shares and 142,332 shares, respectively
                               -732,000                                            
        identified intangible assets, net of accumulated amortization of 33,738 and 31,649, respectively
                                6,044,000                                           
        unallocated common stock held by esop; 142,332 shares and 176,688 shares, respectively
                                -776,000                                           
        identified intangible assets, net of accumulated amortization of 33,219 and 31,649, respectively
                                 6,563,000                                          
        unallocated common stock held by employee stock ownership plan ("esop"); 150,921 shares and 176,688 shares, respectively
                                 -823,000                                          
        indirect automobile loans
                                  6,141,000 7,607,000 11,220,000 19,377,000 353,263,000 376,314,000 510,954,000                                   
        identified intangible assets, net of accumulated amortization of 31,649 and 29,149, respectively
                                  8,133,000                                         
        unallocated common stock held by employee stock ownership plan ("esop"); 176,688 shares and 213,066 shares, respectively
                                  -963,000                                         
        loans and leases held-for-sale
                                   21,109,000 3,190,000 12,482,000 464,000 13,890,000                                    
        identified intangible assets, net of accumulated amortization of 31,028 and 29,149, respectively
                                   8,754,000                                        
        liabilities and equity
                                                                           
        mortgagors’ escrow accounts
                                   8,166,000 7,905,000 7,494,000 8,757,000 8,359,000 7,823,000 6,942,000 7,156,000 6,943,000 6,847,000 6,393,000 6,225,000 6,079,000 5,938,000 6,147,000 5,846,000 6,014,000 5,478,000 5,437,000 5,429,000 5,275,000 5,427,000 5,693,000 5,894,000 5,377,000 5,465,000 5,121,000 5,961,000 4,464,000 4,978,000 4,579,000 5,253,000 4,935,000 4,361,000 4,790,000 4,638,000 4,217,000 4,689,000   
        brookline bancorp, inc. stockholders’ equity:
                                                                           
        accumulated other comprehensive income/
                                   4,896,000 3,352,000                                       
        unallocated common stock held by the employee stock ownership plan ("esop"); 185,787 shares and 213,066 shares, respectively
                                   -1,013,000                                        
        total brookline bancorp, inc. stockholders’ equity
                                   696,371,000 680,417,000  632,400,000 627,663,000 614,039,000 598,865,000 597,531,000 501,890,000 501,077,000 497,582,000 495,257,000 492,416,000 487,317,000 487,511,000 485,641,000                         
        identified intangible assets, net of accumulated amortization of 29,784 and 29,149, respectively
                                    9,998,000                                       
        unallocated common stock held by the employee stock ownership plan ("esop"); 203,973 shares and 213,066 shares, respectively
                                    -1,112,000                                       
        identified intangible assets, net of accumulated amortization of 27,700 and 26,238, respectively
                                     12,082,000                                      
        other assets*
                                     80,111,000                                      
        total assets*
                                     5,782,934,000                                      
        retained earnings, partially restricted*
                                     96,128,000                                      
        unallocated common stock held by the employee stock ownership plan ("esop"); 232,224 shares and 251,382 shares, respectively
                                     -1,266,000                                      
        total brookline bancorp, inc. stockholders’ equity*
                                     653,516,000                                      
        total stockholders' equity*
                                     658,592,000                                      
        total liabilities and stockholders' equity*
                                     5,782,934,000                                      
        (*) previously reported amounts prior to january 1, 2015 have been restated to reflect a retrospective change in accounting principle for investments in qualified affordable housing projects, in accordance with asu 2014-01. refer to note 8, "investments in qualified affordable projects".
                                                                           
        identified intangible assets, net of accumulated amortization of 25,411 and 22,895, respectively
                                      14,371,000                                     
        other real estate owned and repossessed assets
                                      2,463,000 1,246,000 1,248,000 2,765,000 2,647,000                                 
        advances from the fhlbb
                                      1,027,211,000 1,005,644,000 759,675,000 733,394,000                                  
        unallocated common stock held by esop; 261,453 shares and 291,666 shares, respectively
                                      -1,425,000                                     
        identified intangible assets, net of accumulated amortization of 24,583 and 22,895, respectively
                                       15,199,000                                    
        unallocated common stock held by esop; 271,524 shares and 291,666 shares, respectively
                                       -1,480,000                                    
        commercial loans
                                        891,525,000                                   
        identified intangible assets, net of accumulated amortization of 19,437 and 18,272, respectively
                                        20,345,000                                   
        equity:
                                                                           
        brookline bancorp, inc. stockholders’ equity
                                                                           
        preferred stock, 0.01 par value...
                                                                           
        unallocated common stock held by esop; 323,355 shares and 333,918 shares, respectively
                                                                           
        total equity
                                        617,250,000 602,804,000 601,216,000 504,987,000 503,716,000 500,370,000 497,554,000 494,478,000 489,423,000 489,434,000 487,375,000 486,179,000                        
        total liabilities and equity
                                        5,110,378,000 4,972,381,000 4,877,124,000 3,157,498,000 3,114,582,000 3,057,772,000 2,660,396,000 2,659,418,000 2,615,884,000 2,638,914,000 2,641,113,000 2,623,913,000                        
        other securities
                                         500,000 500,000                                 
        total securities
                                         446,324,000 515,552,000                                 
        loans and leases
                                         4,013,129,000 3,935,518,000                                 
        building held-for-sale
                                         6,046,000                                  
        identified intangible assets, net of accumulated amortization of 15,160 and 12,651, respectively
                                         24,578,000                                  
        monies in escrow — bancorp rhode island, inc. acquisition
                                                                           
        money market savings accounts
                                         1,236,967,000 1,174,805,000                                 
        borrowed funds
                                             408,194,000 378,234,000 439,254,000 468,766,000 595,020,000 628,768,000 648,775,000 652,798,000 540,134,000 512,019,000 480,211,000 430,591,000 512,127,000 459,512,000 411,507,000 421,896,000 427,277,000 397,552,000 320,171,000 305,490,000 273,738,000 267,281,000 170,531,000 123,738,000 123,945,000 164,606,000 178,801,000 178,970,000 176,241,000 156,250,000 
        unallocated common stock held by esop; 356,064 shares and 378,215 shares, respectively
                                                                           
        investment securities
                                                                           
        available-for-sale
                                          461,498,000                                 
        building held for sale
                                          6,046,000                                 
        identified intangible assets, net of accumulated amortization of 13,934 and 12,651, respectively
                                          25,849,000                                 
        other borrowings
                                          59,865,000                                 
        unallocated common stock held by esop; 367,137 shares and 378,215 shares, respectively
                                                                           
        securities available for sale
                                           253,510,000 274,448,000 318,597,000 310,664,000 306,504,000 293,023,000 272,933,000 286,744,000 316,268,000 316,052,000 340,273,000 265,424,000 275,884,000 298,776,000 358,029,000 359,879,000 374,906,000 349,813,000 339,189,000 366,374,000 260,852,000 270,432,000 276,489,000 285,768,000 293,222,000 342,964,000 393,017,000 254,834,000 223,327,000 205,116,000 159,623,000 166,893,000 
        loans
                                           2,662,076,000 2,588,923,000 2,524,989,000 2,189,014,000 2,172,465,000 2,164,295,000 2,169,427,000 2,146,311,000 2,124,251,000 1,983,313,000 1,931,323,000 1,892,087,000 1,853,089,000 1,807,053,000 1,803,791,000 1,673,313,000 1,636,755,000 1,620,090,000 1,608,295,000 1,586,884,000 1,269,637,000            
        allowance for loan losses
                                                   -28,943,000                        
        net loans
                                           2,630,948,000 2,558,076,000 2,494,941,000 2,158,652,000 2,141,828,000 2,133,212,000 2,139,301,000 2,116,938,000 2,095,308,000 1,957,591,000 1,906,382,000 1,868,626,000 1,829,777,000 1,783,956,000 1,778,953,000 1,650,835,000 1,614,507,000 1,598,190,000 1,586,120,000 1,565,501,000 1,252,097,000 1,222,765,000 1,166,043,000 1,113,152,000 1,000,810,000 935,678,000 836,087,000 801,043,000 839,829,000 814,648,000 854,033,000 811,161,000 
        accrued interest receivable
                                           9,255,000 9,325,000 9,463,000 8,581,000 8,556,000 9,062,000 8,762,000 8,844,000 8,471,000 8,899,000 9,218,000 9,897,000 9,443,000 9,584,000 9,931,000 9,268,000 9,189,000 8,609,000 8,315,000 8,189,000 5,801,000 5,588,000 5,712,000 5,306,000 5,046,000 5,377,000 5,150,000 5,189,000 5,982,000 5,169,000 5,664,000 5,819,000 
        bank premises and equipment
                                           35,859,000 34,727,000 20,063,000 11,374,000 11,477,000 10,685,000 10,225,000 10,309,000 10,189,000 9,489,000 9,154,000 9,267,000 9,258,000 9,192,000 9,920,000 9,755,000 10,010,000 11,198,000 11,507,000 11,647,000 3,900,000 3,110,000 2,663,000 2,683,000 2,763,000 2,533,000 2,175,000 1,803,000 1,812,000 1,803,000 2,006,000 3,770,000 
        prepaid income taxes
                                           2,498,000 728,000  782,000 371,000   2,587,000  462,000 552,000 1,089,000 3,815,000 1,314,000 2,610,000   1,813,000 2,986,000 1,513,000 270,000 59,000 12,000   1,376,000       
        identified intangible assets, net of accumulated amortization of 12,274 and 11,081, respectively
                                           5,591,000                                
        deposits
                                           2,179,605,000 2,159,133,000 2,118,259,000 1,760,271,000 1,702,658,000 1,633,687,000 1,528,630,000         1,161,555,000 1,168,307,000 1,153,854,000 1,145,995,000 1,143,461,000 773,958,000 735,306,000 725,486,000 709,641,000 667,771,000 662,754,000 663,018,000 632,531,000 671,788,000 640,409,000 614,739,000 618,646,000 
        federal home loan bank advances
                                           437,974,000 421,355,000                               
        unallocated common stock held by esop – 389,763 shares and 424,422 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 11,831 and 11,081, respectively
                                            6,034,000                               
        unallocated common stock held by esop — 401,316 shares and 424,422 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 11,376 and 11,081, respectively
                                             5,569,000                              
        income taxes payable
                                             2,621,000   1,115,000 1,475,000  317,000       327,000 630,000       1,734,000 895,000  10,248,000 4,859,000 5,218,000 9,464,000 4,086,000 3,098,000 
        unallocated common stock held by esop — 412,869 shares and 424,422 shares, respectively
                                                                           
        securities held to maturity
                                              87,000 110,000 112,000 134,000 135,000 159,000 166,000 180,000 195,000 216,000 224,000 354,000 395,000 410,000 841,000 857,000 875,000 889,000 1,198,000 1,222,000 1,272,000 1,411,000 1,548,000 3,717,000 4,887,000 6,921,000 8,547,000 16,981,000 29,304,000 
        identified intangible assets, net of accumulated amortization of 10,775 and 9,857, respectively
                                              2,177,000                             
        unallocated common stock held by esop – 436,469 shares and 472,604 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 10,469 and 9,857, respectively
                                               2,483,000                            
        unallocated common stock held by esop — 448,514 shares and 472,604 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 9,857 and 8,369, respectively
                                                3,095,000                           
        brokered deposits
                                                   26,381,000 27,047,000 67,904,000 67,991,000 77,871,000 77,990,000 68,096,000                  
        unallocated common stock held by esop — 472,604 shares and 522,761 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 9,485 and 8,369, respectively
                                                 3,467,000                          
        unallocated common stock held by esop - 485,141 shares and 522,761 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 9,113 and 8,369, respectively
                                                  3,839,000                         
        retail deposits
                                                  1,500,959,000 1,436,352,000 1,282,114,000 1,311,245,000 1,244,642,000 1,231,252,000 1,235,274,000 1,171,967,000                  
        unallocated common stock held by esop - 497,681 shares and 522,761 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 8,741 and 8,369, respectively
                                                   4,211,000                        
        total liabilities.
                                                   2,137,734,000                        
        unallocated common stock held by esop - 510,221 shares and 522,761 shares, respectively
                                                   -2,781,000                        
        total brookline bancorp, inc. stockholders’ equity.
                                                   484,309,000                        
        identified intangible assets, net of accumulated amortization of 7,494 and 6,618, respectively
                                                    5,458,000                       
        liabilities and stockholders’ equity
                                                                           
        subordinated debt
                                                      7,024,000 7,039,000 12,060,000 12,155,000 12,187,000 12,218,000 12,249,000 12,280,000 12,310,000             
        minority interest in subsidiary
                                                    1,212,000 1,417,000 1,321,000 1,255,000 1,419,000 1,257,000                  
        stockholders’ equity:
                                                                           
        unallocated common stock held by esop – 548,868 shares and 574,974 shares, respectively
                                                                           
        total stockholders’ equity
                                                    505,845,000 507,966,000 531,483,000 547,023,000 567,594,000 591,292,000 590,540,000 602,450,000 601,506,000 613,122,000 612,308,000 585,013,000 585,043,000 596,242,000 596,153,000 604,320,000 614,843,000 613,511,000 637,546,000 296,447,000 289,635,000 288,016,000 286,378,000 
        total liabilities and stockholders’ equity
                                                    2,494,616,000 2,454,340,000 2,391,906,000 2,371,609,000 2,351,494,000 2,381,365,000 2,243,080,000 2,214,704,000 2,207,088,000 2,216,146,000 2,184,994,000 1,694,499,000 1,643,274,000 1,610,218,000 1,591,208,000 1,458,459,000 1,414,208,000 1,424,046,000 1,451,318,000 1,515,442,000 1,129,794,000 1,096,691,000 1,079,058,000 
        identified intangible assets, net of accumulated amortization of 7,056 and 6,618, respectively
                                                     5,896,000                      
        unallocated common stock held by esop – 561,921 shares and 574,974 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 6,115 and 4,604, respectively
                                                      6,837,000                     
        unallocated common stock held by esop – 588,500 shares and 629,081 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 5,611 and 4,604, respectively
                                                       7,341,000                    
        unallocated common stock held by esop — 602,027 shares and 629,081 shares, respectively
                                                                           
        identified intangible assets, net of accumulated amortization of 5,108 and 4,604, respectively
                                                        7,844,000                   
        unallocated common stock held by esop — 615,554 shares and 629,081 shares, respectively
                                                                           
        other investment
                                                          4,723,000 4,662,000 4,545,000 4,527,000 4,438,000 4,456,000 4,453,000 4,318,000 4,256,000 4,166,000 3,969,000 3,917,000 3,844,000 3,923,000 3,772,000 3,622,000 3,505,000 
        deferred income tax asset
                                                         11,679,000                  
        identified intangible assets, net of accumulated amortization of 3,466 and 2,370, respectively
                                                         9,486,000                  
        unearned compensation - recognition and retention plans
                                                                           
        unallocated common stock held by esop - 657,123 shares and 685,161 shares issued, respectively
                                                                           
        core deposit intangible, net of amortization
                                                          8,945,000 9,471,000                
        unallocated common stock held by esop – 671,142 shares and 685,161 shares, respectively
                                                                           
        unallocated common stock held by esop - 685,161 shares and 743,221 shares, respectively
                                                                           
        other real estate owned
                                                            1,150,000 1,400,000 1,400,000           143,000  
        core deposit intangible
                                                            10,064,000 10,656,000 11,249,000             
        unallocated common stock held by esop – 701,623 shares and 743,221 shares, respectively
                                                                           
        unallocated common stock held by esop – 715,489 shares and 743,221 shares, respectively
                                                                           
        unallocated common stock held by esop – 729,355 shares and 743,221 shares, respectively
                                                                           
        unallocated common stock held by esop – 743,221 shares and 803,356 shares, respectively
                                                                           
        loans, excluding money market loan participations
                                                                1,233,926,000 1,177,005,000 1,129,540,000 1,013,764,000 951,489,000 842,811,000 809,199,000 819,043,000 819,860,000 843,294,000 817,143,000 
        money market loan participations
                                                                6,000,000 6,000,000  3,000,000  8,700,000 7,000,000 36,000,000 10,000,000 26,000,000 9,000,000 
        unallocated common stock held by esop – 758,257 shares and 803,356 shares, respectively
                                                                           
        unallocated common stock held by esop – 773,290 shares and 803,356 shares, respectively
                                                                           
        unearned compensation – recognition and retention plans
                                                                           
        unallocated common stock held by esop – 788,323 shares and 803,356 shares, respectively
                                                                           
        unearned compensation - recognition and retention plan
                                                                           
        unallocated common stock held by esop - 818,861 shares and 865,364 shares, respectively
                                                                           
        unallocated common stock held by esop - 834,362 shares and 865,364 shares, respectively
                                                                           
        unallocated common stock held by esop - 849,863 shares and 865,364 shares, respectively
                                                                           
        unallocated common stock held by esop - 877,296 shares and 422,992 shares, respectively
                                                                           
        stock offering subscription proceeds
                                                                       351,946,000    
        unearned compensation — recognition and retention plan
                                                                           
        unallocated common stock held by esop — 408,430 shares and 422,992 shares, respectively
                                                                           
        unallocated common stock held by esop - 415,711 shares and 422,992 shares, respectively
                                                                           
        preferred stock, .01 par value...
                                                                           
        common stock, .01 par value...
                                                                         297,000 296,000 
        unallocated common stock held by esop - 428,708 shares and 455,771 shares, respectively
                                                                           
        unallocated common stock held by esop - 473,729 shares and 455,771 shares, respectively
                                                                           
      Cashflow Statements:
      Quarterly
      Annual
        Unit: USD2025-06-30 2025-03-31 2024-12-31 2024-09-30 2024-06-30 2024-03-31 2023-12-31 2023-09-30 2023-06-30 2023-03-31 2022-12-31 2022-09-30 2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2018-09-30 2018-06-30 2018-03-31 2016-12-31 2016-03-31 2014-09-30 2014-06-30 2013-03-31 2012-06-30 2012-03-31 2011-09-30 2011-06-30 2011-03-31 2010-09-30 2009-12-31 2009-09-30 2009-06-30 2009-03-31 2008-06-30 2008-03-31 2007-09-30 2007-06-30 2007-03-31 2006-09-30 2006-06-30 2006-03-31 2005-12-31 2005-09-30 2005-06-30 2005-03-31 2004-12-31 2004-09-30 2004-06-30 2004-03-31 2003-09-30 2003-06-30 2003-03-31 2002-09-30 2002-06-30 2002-03-31 2001-09-30 
                                                                       
          cash flows from operating activities:
                                                                       
          net income
        22,026,000 19,100,000 17,536,000 20,142,000 16,372,000 14,665,000 22,888,000 22,701,000 21,850,000 7,560,000  30,149,000 25,195,000 24,705,000  28,839,000 31,602,000 26,454,000                       3,675,000 2,694,000 4,250,000 4,852,000 4,941,000   5,397,000 -16,471,970 5,521,000 5,441,000 5,532,000 -13,753,233 4,497,000 4,622,000 4,652,000 4,502,000 6,687,000 -148,000 5,461,000 5,132,000 5,478,000 4,928,000 
          adjustments to reconcile net income to net cash from operating activities:
                                                                       
          provision for credit losses
        7,000,000 5,986,000 4,037,000 4,660,000 5,568,000 7,379,000  3,362,000                                                        
          deferred income tax benefit
                          2,787,000 650,000 -5,269,000 -17,270,000 -803,000 -1,133,000 -2,520,000                                       
          depreciation of premises and equipment
        1,897,000 1,830,000 1,878,000 1,936,000 1,958,000 2,118,000 2,129,000 2,104,000 1,959,000 1,967,000 -3,223,000 1,501,000 1,472,000 1,461,000 -3,181,000 1,487,000 1,487,000 1,318,000 1,208,000 1,253,000 1,444,000 1,581,000 1,966,000 1,827,000 1,801,000 1,760,000 1,783,000 1,791,000 1,940,000 1,476,000                                  
          accretion of investment securities premiums and discounts
        -1,218,000 -1,266,000                                                              
          accretion of premiums and discounts and deferred loan and lease origination costs
        -1,635,000 -1,334,000                                                              
          amortization of identified intangible assets
        1,431,000 1,430,000 1,701,000 1,668,000 1,669,000 1,708,000 1,965,000 1,955,000 1,954,000 1,966,000  120,000 120,000 134,000  208,000 228,000 232,000 312,000 312,000 311,000 336,000 537,000 539,000 467,000 621,000 635,000 828,000 523,000 1,165,000 1,271,000 1,283,000 443,000 454,000 296,000 306,000 372,000 372,000 372,000 372,000 438,000 438,000 504,000 504,000 503,000                   
          amortization of debt issuance costs
        26,000 25,000 25,000 25,000 25,000 25,000 25,000 25,000 25,000 25,000 24,000 26,000 24,000 26,000 25,000 25,000 25,000 25,000 26,000 24,000 25,000 26,000 25,000 25,000 25,000 45,000 25,000                                     
          amortization of acquisition fair value adjustments
        153,000 152,000 277,000 276,000 276,000 484,000 6,239,000 -2,144,000 -2,530,000 -3,176,000                                                      
          gain on sales of loans and leases held-for-sale
        -264,000 -24,000  -415,000    -225,000 -308,000 -1,638,000  -889,000 -291,000 -344,000  -557,000 -538,000 -709,000 -67,000 -632,000 -299,000 -120,000 -535,000 -722,000 -299,000  -905,000 -538,000                                    
          write-down of other repossessed assets
        35,000 281,000  160,000 115,000 22,000  106,000                                                        
          compensation under recognition and retention plans
        872,000 828,000 869,000 815,000 730,000 966,000 1,165,000 915,000 829,000 814,000  784,000 740,000 694,000  584,000 584,000 536,000 451,000 540,000 746,000 624,000 600,000 350,000 682,000 594,000 570,000 408,000 153,000 282,000 153,000 148,000     27,000 40,000 41,000 35,000 529,000 534,000 666,000 776,000 628,000   674,000  668,000 650,000 722,000  722,000 719,000 727,000        
          net change in:
                                                                       
          cash surrender value of bank-owned life insurance
        -519,000 -512,000 -516,000 -512,000 -500,000 -489,000 -485,000 -468,000 -454,000 138,000  -259,000 -255,000 -252,000  69,000 -254,000 -251,000 -240,000 -258,000 -255,000 -254,000 -263,000 -258,000 -254,000 -268,000 -259,000 -286,000                                    
          other assets
        18,330,000 28,931,000 -22,422,000 52,976,000 1,431,000 -25,395,000 67,503,000 -34,045,000 -26,487,000 6,787,000  -58,587,000 -16,425,000 22,908,000  14,762,000 -10,839,000 58,480,000 6,848,000 36,054,000 -16,767,000 -103,913,000 -7,756,000 -6,813,000 -1,397,000 20,206,000 -10,278,000 -1,419,000 -11,831,000 11,683,000   569,000 -3,017,000 5,566,000   294,000 -270,000 686,000 517,000 460,000        -1,026,000 191,000 3,196,000            
          accrued expenses and other liabilities
        -11,600,000 -48,778,000 44,425,000 -56,406,000 3,015,000 11,866,000 -63,852,000 27,224,000 28,121,000 -17,503,000  62,238,000 8,695,000 -35,584,000  -37,210,000 31,634,000 -68,387,000 3,123,000 -27,424,000 -67,148,000 173,346,000 13,997,000 8,083,000 6,143,000 -9,700,000 -8,332,000 4,809,000               247,000 459,000 1,624,000     -233,000 -1,044,000 1,796,000    329,000 1,555,000 -3,000 1,027,000    -1,714,000 
          net cash from operating activities
        33,617,000 8,014,000 43,486,000 24,362,000 28,266,000 8,840,000 39,133,000 28,677,000 30,824,000 17,963,000                                                     8,487,000 
          capital expenditures
                                                            
          free cash flows
        33,617,000 8,014,000 43,486,000 24,362,000 28,266,000 8,840,000 39,133,000 28,677,000 30,824,000 17,963,000                                                     8,487,000 
          cash flows from investing activities:
                                                                       
          proceeds from maturities, calls, and principal repayments of investment securities available-for-sale
        33,531,000 27,179,000 21,442,000 57,653,000 49,237,000 45,664,000 29,605,000 64,574,000 145,176,000 33,064,000  12,140,000 31,110,000 36,251,000  38,302,000 62,335,000 46,184,000 39,502,000 118,875,000 30,664,000 25,530,000 20,592,000 21,937,000 21,632,000                                       
          purchases of investment securities available-for-sale
        -11,086,000 -651,000 -78,620,000 -28,785,000 -39,702,000 -1,369,000 -32,117,000 -51,779,000 -4,569,000 -274,440,000  -38,986,000 -84,135,000  -81,316,000 -22,323,000 -49,514,000 -14,689,000 -50,148,000 -165,406,000 -273,252,000 -24,744,000 -49,108,000 -38,128,000 -41,985,000 -27,824,000                                    
          proceeds from redemption/sales of restricted equity securities
        5,813,000 18,326,000 11,400,000 9,341,000 5,227,000 6,866,000 7,955,000 6,984,000 17,352,000 16,198,000  6,207,000 5,301,000 3,860,000  5,466,000 9,734,000 9,386,000 12,534,000 17,731,000 718,000 2,944,000 6,308,000 1,590,000 1,230,000                                       
          purchase of restricted equity securities
        -4,757,000 -2,708,000 -11,880,000 -13,053,000 -9,481,000 -3,980,000 -20,090,000 -1,023,000 -2,543,000 -27,119,000  -15,561,000 -11,641,000 -3,945,000  -1,937,000   -605,000 -7,808,000 -3,884,000 -17,598,000 -1,928,000 -3,769,000 -6,795,000                                       
          proceeds from sales of loans and leases held-for-investment
        43,549,000 8,000,000 30,610,000 72,224,000   60,086,000 20,605,000 34,500,000 128,942,000  85,053,000 44,184,000 28,093,000  172,087,000 670,000 50,000 567,000 902,000 101,000 5,800,000 1,194,000 2,893,000 285,000 22,863,000 23,116,000                                     
          net decrease in loans and leases
        13,093,000 122,110,000                                                              
          purchase of premises and equipment
          -1,812,000 -513,000 -658,000 -2,002,000 -1,662,000 -2,047,000 -4,874,000 -3,774,000 1,028,000 -2,095,000 -1,693,000 -497,000 1,900,000 -1,082,000 -291,000 -2,347,000 -385,000 -618,000 -835,000 -1,071,000 -699,000 -794,000 -1,827,000 -2,515,000 -796,000 -1,150,000                                    
          proceeds from sales of other repossessed assets
        72,000 122,000  520,000 332,000 309,000  258,000 731,000 89,000                                                      
          net cash from investing activities
        78,762,000 172,859,000 -88,496,000 -7,230,000 -61,631,000 17,754,000  -32,185,000 62,803,000 -412,790,000         161,703,000 83,624,000 -681,503,000 -259,353,000 -33,107,000 -65,793,000 -451,895,000 -88,875,000  -144,035,000            -47,469,000                        
          cash flows from financing activities:
                                                                       
          increase in demand checking, now, savings and money market accounts
        59,372,000 70,532,000        -383,919,000  -95,062,000 -158,671,000 114,131,000  -224,596,000 332,314,000 296,341,000 221,732,000 116,772,000 621,984,000 57,871,000 -82,370,000 -172,177,000 165,925,000 111,194,000 67,160,000 20,841,000 35,085,000 25,508,000                                  
          increase in certificates of deposit and brokered deposits
        -9,734,000 -60,836,000  42,788,000 467,000 184,603,000  42,021,000                                                        
          proceeds from fhlb advances
        324,000,000 222,000,000 356,000,000 535,000,000 437,100,000 315,000,000 1,504,000,000 165,000,000 220,000,000 4,266,000,000                                                      
          repayment of fhlb advances
        -347,179,000 -620,078,000 -345,077,000 -455,076,000 -322,174,000 -388,189,000 -1,180,110,000 -309,109,000 -635,108,000 -4,098,408,000                                                      
          increase in other borrowed funds
        22,368,000 34,025,000 11,341,000 -11,874,000 -47,380,000 58,249,000 -82,356,000           -4,078,000   -15,312,000 10,054,000    11,568,000                                      
          decrease in mortgagors' escrow accounts
        25,000 -611,000 1,419,000 -2,661,000 872,000 -994,000  -4,629,000                                                        
          payment of dividends on common stock
        -12,029,000 -12,029,000 -12,028,000 -12,028,000 -12,001,000 -12,001,000 -11,997,000 -11,990,000 -11,969,000 -11,970,000 -10,374,000 -9,968,000 -10,030,000 -9,705,000 -9,705,000 -9,383,000 -9,383,000 -8,992,000 -9,054,000 -9,093,000 -9,076,000 -9,173,000 -8,043,000 -8,031,000 -6,916,000 -6,348,000 -6,336,000 -5,974,000            -16,499,000                        
          net cash (used for) provided from financing activities
        36,823,000 -366,997,000             590,819,000 -136,978,000 -164,747,000 -326,557,000                                              
          net increase in cash and cash equivalents
        149,202,000 -186,124,000 135,781,000 64,805,000 41,198,000 168,859,000    103,361,000     244,331,000 -81,305,000 189,522,000 -303,990,000 117,584,000 62,417,000 -85,852,000 262,978,000  -28,978,000 23,451,000      83,822,000 26,970,000 -11,392,000 20,867,000 30,498,000 -19,995,000         3,980,000  1,217,000 5,866,000  -31,609,000 37,280,000 7,175,000    10,585,000    -83,465,000    
          cash and cash equivalents at beginning of period
        543,670,000  133,027,000  382,959,000  327,737,000  434,917,000  77,790,000 61,005,000  75,489,000 -24,592,000 117,097,000 106,296,000 65,908,000  121,352,000 153,624,000 152,654,000 118,395,000  136,865,000  144,703,000 242,468,000 88,715,000 
          cash and cash equivalents at end of period
        149,202,000 357,546,000  64,805,000 41,198,000 301,886,000  -63,431,000 -261,888,000 486,320,000  22,182,000 -202,942,000 293,271,000  -81,305,000 189,522,000 130,927,000  62,417,000 -85,852,000 340,768,000 -1,602,000 -28,978,000 84,456,000  73,922,000 8,405,000 -12,363,000 92,096,000 83,822,000 133,266,000 -11,392,000 20,867,000 96,406,000 -19,995,000  -6,837,000 24,460,000 92,267,000 7,975,000 95,901,000 -5,613,000 -5,102,000 156,634,000 -11,541,000 1,217,000 124,261,000  -31,609,000 37,280,000 144,040,000  -20,569,000 -20,901,000 155,288,000 33,446,000 -65,537,000 169,248,000 -83,465,000 370,660,000 86,660,000 14,766,000 
          supplemental disclosure of cash flow information:
                                                                       
          cash paid during the period for:
                                                                       
          interest on deposits, borrowed funds and subordinated debt
        66,386,000 69,004,000 72,531,000 77,112,000 74,552,000 67,233,000 72,357,000 63,828,000 58,426,000 43,785,000  11,044,000 4,899,000 6,331,000  8,354,000 6,565,000 11,007,000 11,490,000 16,443,000 17,350,000 23,227,000 19,387,000 13,866,000 12,880,000 8,615,000 10,447,000 7,840,000 6,299,000 9,139,000 10,333,000 10,778,000              16,016,000    10,213,000              
          income taxes
        11,108,000 1,623,000 2,905,000 3,115,000 6,518,000 547,000 195,000 46,000 5,880,000 2,511,000  6,628,000 10,905,000 2,221,000  10,450,000 9,508,000 2,212,000 3,137,000 13,095,000 11,090,000 2,070,000 4,379,000 9,791,000 928,000 6,821,000 8,286,000 5,199,000 5,876,000 2,614,000 5,504,000 3,771,000 4,662,000 8,868,000 2,012,000 5,325,000 3,115,000 67,000 3,835,000 1,078,000 2,690,000 665,000 382,000 5,673,000 2,120,000 3,271,000 5,780,000 2,927,000  2,615,000 5,839,000 938,000  3,660,000 5,087,000 2,115,000 1,075,000 9,846,000 5,625,000 3,416,000   897,000 
          non-cash investing activities:
                                                                       
          transfer from loans to other repossessed assets
        478,000 217,000  285,000 604,000 454,000  61,000 823,000 251,000  489,000 233,000 691,000                                                  
          deferred income tax expense
         1,365,000 -1,287,000 2,023,000 774,000 -1,101,000 7,969,000 7,988,000 1,680,000 -1,470,000  356,000 577,000 376,000  2,663,000 401,000 1,345,000         -611,000 -479,000 125,000 921,000                                  
          sale of premises and equipment
         481,000                                                              
          transfer from loans and leases to loans held-for-sale
             6,717,000                                                          
          amortization of investment securities deferred
                                                                       
          amortization of premiums and discounts and deferred loan and lease origination costs
          -1,674,000 -1,684,000 -1,609,000 -1,715,000                                                          
          gain on investment securities
               -3,000 -1,701,000      -1,000 7,000 -54,000 -586,000 -1,330,000                                          
          gain on sales of loans and leases
                                                                       
          loss on sales of oreo
                                                                       
          write-down of oreo and other repossessed assets
                   88,000    9,000 36,000 129,000 172,000 34,000 476,000 354,000 123,000 55,000 197,000                                       
          esop shares committed to be released
                   88,000 95,000 111,000  95,000 97,000 83,000 77,000 67,000 59,000 101,000 148,000 142,000 132,000 -20,000 99,000 194,000 128,000 57,000                                  
          proceeds from sales of investment securities available-for-sale
              5,149,000 224,832,000         9,698,000 251,000 45,065,000 86,434,000 1,470,000                                      
          net increase in loans and leases
          -60,074,000 -104,617,000 -73,494,000 -27,734,000 -327,344,000 -69,757,000 -128,119,000 -430,373,000  -214,968,000 -115,482,000 -100,454,000    -995,000 114,468,000 3,764,000 -589,102,000 -96,414,000 -60,067,000 -64,393,000 -386,752,000 -87,889,000 -149,323,000 -137,602,000                                    
          acquisitions, net of cash and cash equivalents acquired
              -80,209,000             467,000 -25,126,000                                       
          proceeds from sales of oreo and other repossessed assets
                   317,000 616,000 427,000  338,000 8,453,000 385,000 613,000 675,000 1,176,000 1,972,000 760,000 388,000 853,000                                       
          increase in certificates of deposit and brokered certificates of deposit
                                                                       
          repurchases of common stock
                         -9,590,000 -10,410,000                                          
          payment of income taxes for shares withheld in share based activity
                                                                    
          net cash from financing activities
          180,791,000 47,673,000 74,563,000 142,265,000 215,986,000 -59,923,000 -355,515,000 498,188,000                                                     13,389,000 
          cash and cash equivalents at beginning of year
                                                                       
          cash and cash equivalents at end of year
                                                                       
          cash paid during the year for:
                                                                       
          transfer from loans to other real estate owned and other repossessed assets
                                                                       
          acquisition of pcsb financial corporation
                                                                       
          fair value of assets acquired, net of cash and cash equivalents acquired
              1,931,528,000             292,025,000                                       
          fair value of liabilities assumed
              1,676,110,000             278,988,000                                       
          common stock issued
              118,000                                                      
          decrease in demand checking, now, savings and money market accounts
             -14,403,000  6,655,000                                                        
          acquisition of pcsb financial corporation:
                                                                       
          amortization of investment securities premiums and discounts
            -1,428,000 -1,693,000  -1,840,000 -2,437,000 -2,473,000  437,000 529,000 646,000  694,000 873,000 770,000 829,000 932,000 664,000 384,000 671,000 368,000 507,000 371,000 500,000 738,000                                    
          provision (credit) for credit losses
                 25,542,000  2,893,000                                                    
          loss on investment securities
                                                                       
          gain on sales of oreo
                                                                       
          equity securities held-for-trading
                         -1,000 1,264,000                                            
          net cash (used for) provided from investing activities
                  332,993,000 -128,907,000 -86,591,000 -120,400,000             -128,835,000                                     
          increase in mortgagors' escrow accounts
                 -837,000  14,000 -9,000 -516,000  224,000 -252,000 582,000    209,000 105,000 -273,000 709,000                                       
          amortization of deferred loan and lease origination costs
               1,019,000 1,099,000 1,063,000  1,129,000 1,359,000 1,438,000  1,442,000 1,473,000 1,584,000 1,649,000 1,754,000 1,759,000 2,154,000 1,770,000 1,792,000 1,625,000 1,445,000 1,453,000 2,534,000 2,565,000 2,426,000 2,608,000 2,563,000                                
          net decrease in cash and cash equivalents
               -63,431,000    22,182,000 -202,942,000 -34,466,000              8,405,000            -29,085,000                        
          decrease in other borrowed funds
                11,208,000 -23,220,000  30,602,000 -21,464,000 -17,790,000           -14,054,000   -3,268,000                                    
          write-down (recovery) of other repossessed assets
                 62,000                                                      
          increase in certificates of deposit
                 750,542,000      202,905,000 -304,399,000 -340,207,000 -103,559,000 235,518,000 -71,689,000 2,333,000 117,456,000 179,771,000 153,091,000 -64,999,000 20,302,000                     8,280,000  46,005,000 44,133,000 54,382,000  9,612,000 11,176,000 5,514,000    -9,581,000 23,444,000 12,542,000  
          net income attributable to parent company
                                                                       
          equity in undistributed income of subsidiaries
                                                                       
          other operating activities
                                                                       
          repayment of esop loan by brookline bank
                                                                       
          pay down of intercompany loan to brookline bank
                                                                       
          proceeds from sale of restricted equity securities
                                                                       
          adjustments to reconcile net income to net cash provided from operating activities:
                                                                       
          amortization (accretion) of acquisition fair value adjustments
                   15,000           -21,000 -973,000 1,185,000                                       
          gain on sales of oreo and other repossessed assets
                                                                      
          net cash provided from operating activities
                   40,089,000 22,122,000 16,144,000  9,984,000 51,892,000 19,418,000 41,717,000 37,707,000 -59,421,000 92,485,000 32,836,000 26,854,000 29,365,000 30,342,000 323,000 37,362,000 16,755,000 14,630,000 13,257,000 8,530,000 15,157,000 2,774,000 18,733,000 11,972,000 4,311,000 15,115,000 4,999,000 11,728,000 10,308,000 11,427,000 11,399,000 8,028,000 12,439,000   7,496,000 -30,728,170 8,685,000 7,198,000 14,866,000 -22,343,369 9,077,000 4,398,000 8,886,000 10,680,000 949,000 4,913,000 6,325,000 484,000 10,190,000  
          decrease in certificates of deposit
                   -63,790,000 -41,250,000 -69,659,000              7,530,000                                    
          proceeds from fhlbb advances
                   1,763,609,000 905,000,000 230,000,000  75,040,000 50,000,000 63,300,000 70,135,000 691,921,000 489,000,000 1,736,600,000 1,331,608,000 1,347,610,000 3,250,390,000 767,962,000 2,244,237,000 491,012,000 877,464,000 729,300,000 802,850,000 690,424,000                                
          repayment of fhlbb advances
                   -1,513,681,000 -798,269,000 -176,671,000  -165,217,000 -224,492,000 -333,503,000 -262,455,000 -1,118,322,000 -358,861,000 -1,357,638,000 -1,363,253,000 -1,339,052,000 -3,157,766,000 -757,513,000 -2,199,504,000 -468,745,000                                    
          net cash provided from (used for) financing activities
                     69,790,000             126,945,000              38,362,000 30,468,000             17,567,000 61,144,000        
          credit for benefit from credit losses
                     -164,000                                                  
          accretion of acquisition fair value adjustments
                     -3,000  -16,000 3,000 -51,000  -14,000 -17,000 -372,000    -855,000 -789,000 -2,226,000            -33,000                        
          (recovery) write-down of oreo and other repossessed assets
                     -8,000                                                  
          net cash provided from (used for) operating activities
                                                                       
          pay down (issuance) of intercompany loan to brookline bank
                                                                       
          net cash provided from (used for) investing activities
                      -342,785,000 45,689,000 302,377,000 3,149,000              7,435,000             20,905,000                   
          common stock issued for acquisition
                              55,181,000                                       
          redemption of noncontrolling interest in subsidiary
                                                                       
          payment of dividends to owners of noncontrolling interest in subsidiary
                              -403,000 -782,000 -708,000 -530,000 -255,000                                    
          (credit) benefit from credit losses
                       -3,110,000 -3,331,000 -2,147,000                                              
          proceeds from maturities, calls, and principal repayments of investment securities held to maturity
                          6,302,000 733,000 632,000 1,158,000                                       
          net decrease (increase) in loans and leases
                       -86,169,000                                                
          transfer from loans to other real estate owned
                       576,000 370,000 382,000 5,887,000 668,000 1,068,000 1,733,000 465,000 832,000 594,000 1,269,000 807,000 3,435,000 5,160,000 1,465,000                                  
          (decrease) in other borrowed funds
                                                                       
          net income attributable to brookline bancorp, inc.
                          26,663,000 18,677,000 19,571,000 -17,276,000 22,460,000 20,831,000 18,633,000 13,279,000 12,812,000 11,581,000 11,585,000 8,813,000 7,529,000 6,349,000 6,276,000 7,000,000 7,267,000 7,038,000 5,836,000 5,243,000 4,677,000 3,444,000                        
          net income attributable to noncontrolling interest in subsidiary
                              774,000 898,000 795,000  830,000 662,000 471,000 427,000 254,000 285,000 307,000 326,000 283,000 235,000 183,000 187,000 126,000 39,000                        
          benefit from credit losses
                          -2,103,000 4,528,000 5,347,000 54,114,000 2,717,000 1,470,000 641,000 3,215,000 2,378,000 2,034,000 2,864,000 1,855,000 6,678,000 3,247,000 891,000 839,000 1,059,000 551,000 2,630,000 2,473,000 1,876,000 2,801,000 2,579,000 2,114,000                      
          origination of loans and leases held-for-sale
                              -6,638,000 -5,450,000 -7,198,000 -20,512,000 -11,949,000                                     
          proceeds from sales of loans and leases held-for-sale
                              7,233,000 5,823,000 9,362,000                                       
          purchases of investment securities held-to-maturity
                              -8,915,000 -11,122,000 -3,496,000                                    
          proceeds from exercise of stock options
                                            2,000     419,000          338,000          
          proceeds from issuance of noncontrolling units
                              1,000 129,000 76,000                                    
          net cash provided from financing activities
                          -85,836,000 -58,914,000 655,072,000 429,846,000 -1,331,000 9,961,000 445,981,000 61,643,000  115,078,000   92,731,000 11,005,000 34,063,000 54,028,000 77,254,000   -10,737,000 13,748,000 6,656,000       30,435,000 24,572,000  -14,365,000 25,881,000 24,638,000        -68,560,000 380,975,000 19,122,000  
          acquisition of first commons bank, n.a.:
                                                                       
          loss on sales of oreo and other repossessed assets
                                                                       
          increase increase in other borrowed funds
                                                                       
          (decrease) in mortgagors' escrow accounts
                           -38,000                                            
          brookline bancorp, inc. and subsidiariesunaudited consolidated statements of cash flows
                                                                       
          proceeds from issuance of common stock
                                                                       
          gain on sales of investment securities
                              -1,162,000                                       
          equity securities held for trading
                                                                       
          net (decrease) in cash and cash equivalents
                                                                       
          transfer from loans and leases held-for-sale to loans and leases
                                  10,000,000                                     
          net income attributable to noncontrolling interest insubsidiary
                                                                       
          gain on sales/disposals of premises and equipment
                                                                       
          proceeds from redemption of restricted equity securities
                                 2,806,000 679,000   2,108,000                                  
          proceeds from sales of premises and equipment
                                                                      
          brookline bancorp, inc. and subsidiariesconsolidated statements of cash flows
                                                                       
          proceeds from issuance of subordinated notes
                                                                       
          transfer from loans and leases to loan and leases held-for-sale
                                                                       
          proceeds from loans and leases held-for-sale
                                  12,323,000                                     
          deferred income tax (benefit) expense
                                                                       
          gain on sales of oreo and repossessed assets
                                                                       
          write-down of oreo and repossessed assets
                                  45,000                                     
          proceeds from maturities, calls and principal repayments of investment securities available-for-sale
                                  27,639,000 25,899,000 2,273,000 31,789,000                                  
          proceeds from maturities, calls, and principal repayments of investment securities held-to-maturity
                                  13,784,000                                    
          purchases of restricted equity securities
                                   -3,358,000                                    
          proceeds from sales of oreo and repossessed assets
                                  1,547,000                                     
          increase in mortgagors’ escrow accounts
                                   398,000 -407,000 877,000   96,000 454,000 3,000 146,000 -209,000 301,000 -168,000 359,000 41,000 386,000 154,000 -152,000 313,000 -113,000 -201,000 517,000    315,000  399,000 -674,000 688,000 574,000      406,000 
          supplemental disclosures of cash flows information:
                                                                       
          transfer from loans and leases to loans and leases held-for-sale
                                                                       
          loss on sales of oreo and repossessed assets
                                  -7,000                                     
          increase/(decrease) in other borrowed funds
                                  1,151,000                                     
          increase/(decrease) in mortgagors’ escrow accounts
                                  389,000                                     
          net (increase)/decrease in cash and cash equivalents
                                  -1,567,000                                     
          cash flows resulting from the sale of the indirect automobile portfolio and the oreo and repossessed assets which had been recorded as cash provided from operating activities has been revised to cash flows from investing activities in the first quarter of 2015 to properly reflect the cash flow activity. there is no impact to the company's net income or related per share amounts for the three months ended march 31, 2015.
                                                                       
          gain on sale/disposals of premises and equipment
                                                                       
          loss on sales of investment securities
                                                                      
          net cash provided from/(used for) investing activities
                                                                       
          increase/(decrease) in certificates of deposit
                                                                       
          (decrease)/increase in mortgagors’ escrow accounts
                                                                       
          net cash (used for)/provided from financing activities
                                                                       
          net increase/(decrease) in cash and cash equivalents
                                                                       
          previously reported amounts prior to january 1, 2015 have been restated to reflect a retrospective change in accounting principle for investments in qualified affordable housing projects, in accordance with asu 2014-01. refer to note 8, "investments in qualified affordable projects".
                                                                       
          cash flows resulting from the sale of the indirect automobile portfolio and the oreo and repossessed assets which had been recorded as cash provided from operating activities in the prior filings have been revised to cash flows from investing activities in the second quarter to properly reflect the cash flow activity. there is no impact to the company's net income or related per share amounts for the six months ended june 30, 2015 and june 30, 2014.
                                                                       
          origination of loans and leases to be sold
                                   -2,281,000                                    
          proceeds from loans and leases sold
                                   16,245,000   33,952,000 22,766,000                                
          proceeds from sales of other real estate owned and repossessed assets
                                   2,171,000                                    
          (loss)/gain on sales of other real estate owned and repossessed assets
                                                                       
          write-down of other real estate owned and repossessed assets
                                   46,000 -566,000 755,000                                  
          income from investments in affordable housing projects
                                   543,000                                    
          repayment of subordinated debentures
                                                                       
          gain on sales of other real estate owned and repossessed assets
                                                                       
          (gain)/loss on sale/disposals of premises and equipment
                                                                       
          repayment of subordinated debt
                                     3,000,000                                  
          supplemental disclosures of cash flow information:
                                                                       
          proceeeds from loans and leases sold
                                     14,886,000                                  
          amortization of securities premiums and discounts
                                     913,000 1,895,000 807,000                                
          gain on sale of loans held for sale
                                                                       
          gains on sales of other real estate owned and repossessed assets
                                                                       
          loss on investments in affordable housing projects
                                     312,000                                  
          monies in escrow — bancorp rhode island, inc. acquisition
                                      112,983,000                                
          proceeds from sales of other real estate owned
                                     978,000                                  
          acquisition of bancorp rhode island, inc.:
                                                                       
          assets acquired
                                        402,000 245,752,000               18,000 -1,008,000 472,402,000            
          liabilities assumed
                                        402,000 251,544,000               420,351,000            
          income from bank-owned life insurance
                                                                       
          depreciation and amortization of premises and equipment
                                      801,000 895,000                                
          non-accretable discount recognized as interest income
                                                                       
          gain on sale of securities
                                                                       
          write-down of acquired assets
                                                                       
          release of esop shares
                                      61,000 60,000 96,000 106,000 123,000 114,000 120,000 134,000 124,000 115,000 137,000 131,000 157,000 164,000 175,000   211,000  222,000 212,000 213,000  225,000 217,000 234,000 235,000 212,000 196,000 188,000 179,000 121,000 140,000 
          deferred income taxes
                                       985,000    8,000 994,000   110,000    -285,000 419,000   582,000    144,000  -450,000 -215,000 798,000    -233,000 -23,000 421,000  
          increase in:
                                                                       
          decrease in:
                                                                       
          securities available-for-sale:
                                                                       
          proceeds from sales
                                                                       
          proceeds from maturities, calls and principal repayments
                                                                       
          purchases
                                                                       
          purchase of other securities
                                                                       
          redemption of restricted securities
                                      2,003,000                                
          increase in demand deposits and now, savings and money market savings accounts
                                      73,959,000 106,122,000 34,445,000 56,208,000 108,039,000 50,460,000  56,132,000 56,332,000 40,405,000 11,466,000 17,558,000  -2,998,000 3,263,000     -37,963,000     4,669,000 24,206,000 8,411,000 14,183,000 20,444,000  7,935,000 6,947,000  
          increase in other borrowings
                                                                       
          income tax benefit from vesting of recognition and retention plan shares and dividend distributions on allocated esop plans
                                                                       
          expense of stock options granted
                                        3,000 5,000 37,000                             
          payment of dividend to owners of noncontrolling interest in subsidiary
                                                                       
          purchase of additional ownership interest in subsidiary
                                                                       
          acquisition of first ipswich bancorp:
                                                                       
          securities available for sale:
                                                                       
          proceeds from principal repayments
                                       67,849,000                                
          purchase of securities, other
                                                                       
          proceeds from payment of federal funds purchased
                                                                       
          decrease in other borrowings
                                       21,514,000                                
          increase in other financing activities
                                       643,000                                
          nonaccretable discount recognized as interest income
                                                                       
          depreciation and amortization
                                        559,000 521,000 410,000 408,000  382,000 458,000 334,000 326,000 338,000 367,000 365,000 360,000   348,000  368,000 404,000 387,000  174,000 171,000 177,000 172,000 162,000 141,000 134,000 134,000 137,000 284,000 
          net amortization of securities premiums and discounts
                                        583,000 589,000 573,000 534,000                            
          amortization of deferred loan origination costs
                                        2,464,000 2,395,000 2,359,000 2,347,000 2,275,000 2,359,000 2,335,000 2,379,000 2,697,000 2,664,000 2,683,000 2,515,000 2,355,000   1,874,000  1,676,000 1,549,000 1,311,000  1,303,000 1,164,000 1,047,000        
          amortization of mortgage servicing rights
                                        6,000 5,000 6,000 3,000 4,000 7,000 11,000 10,000 4,000 6,000 6,000 7,000 3,000   9,000  22,000 14,000 15,000            
          gain on sales of securities
                                                                       
          loss on impairment of securities
                                                                      
          write-down of other real estate owned
                                               27,000 40,000                      
          write-down of assets acquired
                                        22,000 57,000 55,000 53,000                            
          compensation under recognition and retention plan
                                        135,000 43,000 59,000 20,000                     40,000 26,000 40,000 53,000 40,000 41,000 42,000 
          accrued interest receivable
                                        70,000   -25,000    364,000 319,000 405,000 -454,000 141,000 726,000              74,000    155,000 
          prepaid income taxes
                                          78,000    193,000 90,000 1,553,000   487,000     1,173,000 -1,473,000 1,852,000            
          income taxes payable
                                           -360,000                   245,000   155,000 -359,000 -4,246,000 6,385,000 988,000 
          proceeds from sales of securities available for sale
                                          26,320,000 21,188,000          903,000  291,000 9,478,000    627,000        
          proceeds from principal repayments of securities available for sale
                                        35,415,000 49,556,000 25,777,000 61,130,000                            
          proceeds from principal repayments of securities held to maturity
                                           23,000                            
          purchase of securities available for sale
                                               -54,718,000                        
          net increase in loans
                                               -23,207,000                        
          sale of other real estate owned
                                                                       
          acquisition, net of cash and cash equivalents acquired
                                        5,792,000                             
          purchase of bank premises and equipment
                                               -321,000                        
          proceeds from federal home loan bank advances
                                                                       
          repayment of federal home loan bank advances
                                                                       
          proceeds from federal funds purchased
                                                                       
          income tax benefit from vesting of recognition and retention plan shares and payment of dividend distributions on allocated esop shares
                                                                       
          purchase of additional interest in subsidiary
                                                                      
          interest on deposits and borrowed funds
                                        7,763,000 8,766,000 8,070,000 8,493,000  12,890,000 15,436,000 15,599,000 18,457,000 18,005,000 17,951,000 18,940,000 16,835,000   12,481,000    7,713,000  5,350,000 5,030,000 4,750,000 4,370,000 4,594,000 4,906,000 6,836,000 6,615,000 6,626,000 7,956,000 
          net amortization of acquisition fair value adjustments
                                                                       
          proceeds from federal home loan bank of boston advances
                                         1,264,500,000 918,000,000 79,400,000 746,500,000 4,095,500,000 3,195,240,000 3,777,000,000 432,400,000 108,540,000 181,000,000 345,500,000 213,000,000 1,149,500,000 951,000,000 597,000,000  68,000,000 268,200,000 245,400,000  132,000,000 111,700,000 246,000,000    4,000,000 20,000,000 
          repayment of federal home loan bank of boston advances
                                               -3,865,636,000                        
          income tax benefit from vesting of recognition and retention plan shares and dividend distributions on allocated esop shares
                                                                       
          impairment losses on securities
                                                                       
          increase in income taxes payable
                                          3,042,000     350,000                        
          decrease in accrued expenses and other liabilities
                                                                       
          proceeds from sale of securities of securities available for sale
                                          124,000                             
          repayment of federal funds purchased
                                                                       
          repayment of other borrowings
                                                                       
          increase in certificates of deposit excluding brokered deposits
                                                                       
          decrease in brokered certificates of deposit
                                                                       
          income tax benefit from vesting of recognition and retention plan shares, exercise of non-incentive stock options, payment of dividend equivalent rights and dividend distributions on allocated esop shares
                                           -1,000 303,000 365,000 666,000                        
          stock options granted
                                           76,000 54,000                           
          payment of dividend equivalent rights
                                               -403,000                        
          net cash provided from financing activities activities
                                                                       
          depreciation and amortization of bank premises and equipment.
                                                                       
          accretion, net of amortization, of securities premiums and discounts
                                                                       
          net accretion of acquisition fair value adjustments
                                                                       
          impairment loss on securities
                                            18,000 726,000                        
          (gain) income from sales of securities
                                                                       
          proceeds from redemptions and maturities of securities available for sale
                                            22,681,000 33,100,000 41,648,000 30,775,000 56,207,000 9,786,000 13,741,000 30,394,000 79,609,000   27,590,000  58,366,000 66,936,000 39,594,000  40,737,000 39,882,000 16,055,000 109,291,000 61,598,000 26,541,000 30,571,000 17,831,000 10,629,000 13,238,000 
          proceeds from redemptions and maturities of securities held to maturity
                                            22,000 1,000 24,000 2,000 14,000 9,000 21,000 8,000 9,000   15,000  16,000 19,000 13,000  24,000 50,000 70,000 137,000 2,169,000 1,142,000 2,033,000 1,625,000 1,067,000 12,311,000 
          (purchase) redemption of federal home loan bank of boston stock
                                                                       
          sales of other real estate owned
                                                                       
          increase in demand deposits and now, savings and money market savings accounts.
                                                                       
          increase
                                                                       
          decrease in brokered deposits
                                                                       
          purchase of treasury stock
                                                                       
          payment of dividends to minority owners of subsidiary
                                                                       
          proceeds from issuance of units of ownership to minority owners of subsidiary
                                                                       
          transfer of loans to other real estate owned
                                                                       
          net amortization (accretion) of securities premiums and discounts
                                             410,000                          
          purchase of federal home loan bank of boston stock
                                                    2,004,000                   
          deferred tax assets
                                                                       
          increase in retail certificates of deposit
                                              8,275,000 68,103,000 -40,597,000 43,351,000 30,167,000 -1,011,000 21,818,000 40,531,000                  
          reload stock options granted
                                              33,000 93,000 38,000 59,000                      
          net accretion of securities premiums and discounts
                                               -44,000                        
          increase in accrued expenses and other liabilities
                                               -153,000  95,000                      
          proceeds from calls of securities available for sale
                                                                       
          redemption of federal home loan bank of boston stock
                                                                       
          exercise of stock options
                                               2,568,000  699,000   358,000       9,000    530,000   1,137,000 162,000 44,000 220,000  
          loss on write-down of securities
                                                1,249,000                      
          minority interest in earnings of subsidiary
                                                63,000 46,000 66,000 44,000 44,000                   
          proceeds from redemptions of federal home loan bank of boston stock
                                                                      
          income tax benefit from dividend payments on unexercised stock options and allocated esop shares
                                                   216,000 94,000                   
          payment of dividend to minority interest members of subsidiary
                                                                       
          decrease (increase) in:
                                                                       
          proceeds from sales or calls of securities available for sale
                                                 3,275,000                      
          purchase (redemption) of federal home loan bank of boston stock
                                                                       
          income tax benefit from vested recognition and redemption plan shares and dividend payments on unexercised stock options and allocated esop shares
                                                 528,000                      
          benefit from loan losses
                                                  1,503,000 1,108,000 1,249,000   748,000  32,000 957,000 654,000  635,000 711,000 330,000       275,000 
          net gains from sales of securities
                                                                       
          equity interest in earnings of other investment
                                                                  60,000     
          decrease in demand deposits and now, savings and money market savings accounts
                                                     -24,737,000                  
          increase in brokered certificates of deposit
                                                     10,000,000                  
          repayment of other borrowed funds of subsidiary
                                                                       
          income tax benefit from vested recognition and retention plan shares and dividend payments on unexercised stock options and allocated esop shares
                                                                       
          acquisition of eastern funding llc:
                                                                       
          minority interest in subsidiary
                                                                      
          amortization, net of accretion, of securities premiums and discounts
                                                       79,000  366,000 615,000 690,000  991,000 716,000 1,282,000 1,468,000 3,231,000 1,171,000 421,000 295,000 144,000 57,000 
          swap agreement market valuation credit
                                                                       
          income tax benefit from dividend payments on unvested recognition and retention plan shares and allocated esop shares and the exercise of non-incentive stock options
                                                                       
          purchase of securities held to maturity
                                                                       
          proceeds from sales of participations in loans
                                                         253,000 29,185,000     5,318,000 59,000 2,990,000 -2,615,000 2,990,000  
          distribution from other investment
                                                         92,000 147,000  -1,000 144,000 128,000 1,000 241,000 2,000 193,000 69,000  
          acquisition of mystic financial, inc.:
                                                                       
          income tax benefit from recognition and retention plan shares,dividend payments on unvested recognition and retention plan shares and allocated esop shares, and payment of dividend equivalent rights
                                                                       
          net income as reported
                                                                       
          total stock-based compensation expense determined using fair value accounting for stock option awards, net of taxes
                                                                       
          dividends on unvested restricted stock awards
                                                                       
          pro forma net income
                                                                       
          earnings per share:
                                                                       
          as reported
                                                                       
          pro forma
                                                                       
          amortization of core deposit intangible
                                                       526,000  593,000 592,000 593,000            
          income tax benefit from recognition and retention plan shares, dividend payments on unvested recognition and retention plan shares and allocated esop shares, and payment of dividend equivalent rights
                                                       224,000                
          equity in undistributed net (income) loss of subsidiaries
                                                                       
          increase in prepaid income taxes
                                                                       
          decrease (increase) in other assets
                                                                       
          investment in subsidiaries
                                                                       
          distribution from subsidiaries
                                                                       
          repayment of esop loan by subsidiary bank
                                                                       
          loan to subsidiary bank
                                                                       
          repayment of loan by subsidiary bank
                                                                       
          payment from subsidiary bank for shares vested in recognition and retention plans
                                                                       
          dividend distribution from other investment
                                                                       
          net cash provided from investing activities
                                                                       
          income tax benefit from exercise of non-incentive stock options and dividend payments on unvested recognition and retention plan shares and allocated esop shares
                                                                       
          cash paid during the year for income taxes
                                                                       
          interest on subordinated debt
                                                                       
          gains from sales of securities
                                                                       
          income tax benefit from exercise of non-incentive stock options, recognition and retention plan shares and dividends paid to esop participants
                                                         242,000 665,000            
          decrease (increase) in prepaid income taxes
                                                                       
          increase in other assets
                                                                       
          net proceeds from issuance of common stock
                                                                       
          income tax benefit from exercise of non-incentive stock options
                                                                       
          income tax benefit from exercise of non-incentive stock options, dividend paid to esop participants and recognition and retention plan shares
                                                                       
          proceeds from sales and calls of securities available for sale
                                                                1,156,000 925,000 538,000 560,000 1,228,000 1,083,000 
          income tax benefit from exercise of non-incentive stock options and dividend paid to esop participants
                                                                1,000       
          retroactive assessment related to reit
                                                                  5,515,000     
          income tax benefit from exercise of non-incentive stock options and recognition and retention plan shares
                                                               74,000        
          provision (credit) for loan losses
                                                                240,000 360,000 375,000     
          amortization
                                                                369,000 146,000 33,000     
          net gains from sales and repayment of securities
                                                                       
          swap agreement market valuation (credit) charge
                                                                       
          prepayment of federal home loan bank of boston advances
                                                                       
          net proceeds from stock offering subscription
                                                                       
          cash payment in lieu of fractional shares in reorganization exchange of shares
                                                                       
          transfer of net assets from brookline bancorp, mhc
                                                                       
          stock offering subscription proceeds
                                                                       
          increase in mortgagors’ escrow deposits
                                                                  534,000   322,000  
          cash (received) paid during the period for:
                                                                       
          write-off of premises and equipment included in restructuring charge
                                                                       
          accretion of deferred loan origination fees and unearned discounts
                                                                       
          write-down in carrying value of a debt security available for sale
                                                                       
          swap agreement market valuation charge
                                                                   146,000    
          net decrease (increase) in loans
                                                                   6,870,000 3,483,000 5,554,000  
          increase in demand deposits, now, savings and money market savings accounts
                                                                       
          net gains from sales of securities available for sale
                                                                       
          net gains from sales of other real estate owned
                                                                       
          swap market valuation charge
                                                                       
          proceeds from sales of participation in loans
                                                                       
          purchase of common stock for esop