Brookline Bancorp (BRKL) 10-K 28 Feb 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 28, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	0-23695
Entity Registrant Name	BROOKLINE BANCORP, INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3402944
Entity Address, Address Line One	131 Clarendon Street
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
City Area Code	617
Local Phone Number	425-4600
Title of 12(b) Security	Common Stock, par value of $0.01 per share
Trading Symbol	BRKL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1.2
Entity Common Stock, Shares Outstanding		79,767,595
Entity Central Index Key	0001049782
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
ASSETS
Cash and due from banks	$ 33,589	$ 47,542
Short-term investments	44,201	42,042
Total cash and cash equivalents	77,790	89,584
Investment securities available-for-sale	498,995	502,793
Investment securities available-for-sale		502,793
Investment securities held-to-maturity (fair value of $87,561 and $112,830, respectively)	86,780	114,776
Equity securities held-for-trading	3,581	4,207
Total investment securities	589,356	621,776
Loans held-for-sale	0	3,247
Total loans and leases	6,737,816	6,303,516
Allowance for loan and lease losses	(61,082)	(58,692)
Net loans and leases	6,676,734	6,244,824
Restricted equity securities	53,818	61,751
Premises and equipment, net of accumulated depreciation of $76,763 and $70,140 respectively	74,350	76,382
Right-of-use asset operating leases	24,876
Deferred tax asset	25,017	21,495
Goodwill	160,427	160,427
Identified intangible assets, net of accumulated amortization of $37,481 and $35,818, respectively	4,423	6,086
Other real estate owned (OREO) and repossessed assets, net	2,631	4,019
Other assets	167,431	103,214
Total assets	7,856,853	7,392,805
Non-interest-bearing deposits:
Demand checking accounts	1,141,578	1,033,551
Interest-bearing deposits:
NOW accounts	371,380	336,317
Savings accounts	613,467	619,961
Money market accounts	1,682,005	1,675,050
Certificate of deposit accounts	2,021,642	1,789,165
Total interest-bearing deposits	4,688,494	4,420,493
Total deposits	5,830,072	5,454,044
Borrowed funds:
Advances from the Federal Home Loan Bank of Boston (FHLBB)	758,469	784,375
Subordinated debentures and notes	83,591	83,433
Other borrowed funds	60,689	52,734
Total borrowed funds	902,749	920,542
Operating lease liabilities	24,876
Mortgagors' escrow accounts	7,232	7,426
Accrued expenses and other liabilities	146,318	100,174
Total liabilities	6,911,247	6,482,186
Commitments and contingencies
Brookline Bancorp, Inc. stockholders' equity:
Common stock, $0.01 par value; 200,000,000 shares authorized; 85,177,172 shares issued and 85,177,172 shares issued, respectively	852	852
Additional paid-in capital	736,601	755,629
Retained earnings, partially restricted	265,376	212,838
Accumulated other comprehensive loss	2,283	(9,460)
Treasury stock, at cost; 5,003,127 shares and 5,020,025 shares, respectively	(59,073)	(59,120)
Unallocated common stock held by ESOP; 79,548 shares and 109,950 shares, respectively	(433)	(599)
Total Brookline Bancorp, Inc. stockholders' equity	945,606	900,140
Noncontrolling interest in subsidiary	0	10,479
Total stockholders' equity	945,606	910,619
Total liabilities and stockholders' equity	7,856,853	7,392,805
Commercial real estate loans
ASSETS
Total loans and leases	3,669,222	3,351,736
Commercial loans and leases
ASSETS
Total loans and leases	1,838,748	1,768,958
Consumer loans
ASSETS
Total loans and leases	$ 1,229,846	$ 1,182,822

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Investment securities held to maturity, fair value	$ 87,561	$ 112,830
Premises and equipment, accumulated depreciation and amortization	76,763	70,140
Identified intangible assets, accumulated amortization	$ 37,481	$ 35,818
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	85,177,172	85,177,172
Treasury stock, shares	5,003,127	5,020,025
Unallocated common stock held by ESOP, shares	79,548	109,950

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest and dividend income:
Loans and leases	$ 330,345	$ 295,269	$ 247,022
Debt securities	12,281	13,960	12,524
Marketable and restricted equity securities	3,477	3,964	3,062
Short-term investments	1,523	700	442
Total interest and dividend income	347,626	313,893	263,050
Interest expense:
Deposits	69,615	41,978	23,288
Borrowed funds	24,711	24,216	16,581
Total interest expense	94,326	66,194	39,869
Net interest income	253,300	247,699	223,181
Provision for credit losses	9,583	4,951	18,988
Net interest income after provision for credit losses	243,717	242,748	204,193
Non-interest income:
Loan level derivative income, net	8,262	5,440	2,187
Gain on investment securities, net	508	227	11,393
Gain on sales of loans and leases held-for-sale	1,709	1,883	2,644
Other	6,594	5,847	4,789
Total non-interest income	29,793	25,224	32,173
Non-interest expense:
Compensation and employee benefits	96,554	91,535	82,413
Occupancy	15,696	14,991	14,546
Equipment and data processing	18,652	18,213	16,854
Professional services	4,366	4,404	4,315
FDIC insurance	1,445	2,722	3,326
Advertising and marketing	4,044	4,016	3,369
Amortization of identified intangible assets	1,663	2,080	2,089
Merger and acquisition expense	1,125	3,787	411
Other	13,936	13,484	11,788
Total non-interest expense	157,481	155,232	139,111
Income before provision for income taxes	116,029	112,740	97,255
Provision for income taxes	28,269	26,189	43,636
Net income before noncontrolling interest in subsidiary	87,760	86,551	53,619
Less net income attributable to noncontrolling interest in subsidiary	43	3,489	3,101
Net income attributable to Brookline Bancorp, Inc.	$ 87,717	$ 83,062	$ 50,518
Earnings per common share:
Basic (in dollars per share)	$ 1.10	$ 1.04	$ 0.68
Diluted (in dollars per share)	$ 1.10	$ 1.04	$ 0.68
Weighted average common shares outstanding during the year:
Basic (in shares)	79,679,781	79,669,668	74,459,508
Diluted (in shares)	79,856,921	79,909,251	74,811,408
Dividends declared per common share (in dollars per share)	$ 0.450	$ 0.395	$ 0.360
Deposit fees
Non-interest income:
Non-interest income, fees	$ 10,623	$ 10,400	$ 10,050
Loan fees
Non-interest income:
Non-interest income, fees	$ 2,097	$ 1,427	$ 1,110

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income before noncontrolling interest in subsidiary	$ 87,760	$ 86,551	$ 53,619
Investment securities available-for-sale:
Unrealized securities holding gains (losses)	15,290	(4,444)	(1,274)
Income tax (expense) benefit	(3,379)	980	457
Net unrealized securities holding gains (losses) before reclassification adjustments	11,911	(3,464)	(817)
Less reclassification adjustments for securities gains included in net income:
Gain on sales of securities, net	0	173	0
Income tax expense	0	(38)	0
Net reclassification adjustments for securities gains included in net income	0	135	0
Net unrealized securities holding losses	11,911	(3,599)	(817)
Postretirement benefits:
Adjustment of accumulated obligation for postretirement benefits	(227)	121	(422)
Income tax benefit (expense)	59	(32)	170
Net adjustment of accumulated obligation for postretirement benefits	(168)	89	(252)
Other comprehensive loss, net of taxes	11,743	(3,510)	(1,069)
Comprehensive income	99,503	83,041	52,550
Net income attributable to noncontrolling interest in subsidiary	43	3,489	3,101
Comprehensive income attributable to Brookline Bancorp, Inc.	$ 99,460	$ 79,552	$ 49,449

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Total Brookline Bancorp, Inc. Stockholders' Equity	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Unallocated Common Stock Held by ESOP	Noncontrolling Interest in Subsidiary
Balance beginning of period at Dec. 31, 2016	$ 702,749	$ 695,544	$ 757	$ 616,734	$ 136,671	$ (3,818)	$ (53,837)	$ (963)	$ 7,205
Increase (Decrease) in Stockholders' Equity
Reclassification due to the adoption of ASU No. 2018-02					1,063	(1,063)
Net income attributable to Brookline Bancorp, Inc.	50,518	50,518			50,518
Net income attributable to noncontrolling interest in subsidiary	3,101								3,101
Issuance of common stock	81,943	81,943	60	81,883
Issuance of noncontrolling interest	118								118
Other comprehensive income (loss)	(1,069)	(1,069)				(1,069)
Common stock dividends	(27,035)	(27,035)			(27,035)
Dividend distribution to owners of noncontrolling interest in subsidiary	(1,671)								(1,671)
Compensation under recognition and retention plans	3,428	3,428		1,045			2,383
Common stock held by ESOP committed to be released	501	501		314				187
Balance end of period at Dec. 31, 2017	812,583	803,830	817	699,976	161,217	(5,950)	(51,454)	(776)	8,753
Increase (Decrease) in Stockholders' Equity
Reclassification due to the adoption of ASU No. 2018-02						0
Net income attributable to Brookline Bancorp, Inc.	83,062	83,062			83,062
Net income attributable to noncontrolling interest in subsidiary	3,489								3,489
Common stock issued for acquisition	55,183	55,183	35	55,148
Issuance of noncontrolling interest	130								130
Other comprehensive income (loss)	(3,510)	(3,510)				(3,510)
Common stock dividends	(31,441)	(31,441)			(31,441)
Dividend distribution to owners of noncontrolling interest in subsidiary	(1,893)								(1,893)
Restricted stock awards, net of awards surrendered	2,473	2,473		139			2,334
Treasury stock, repurchase shares	(10,000)	(10,000)					(10,000)
Common stock held by ESOP committed to be released	543	543		366				177
Balance end of period at Dec. 31, 2018	910,619	900,140	852	755,629	212,838	(9,460)	(59,120)	(599)	10,479
Increase (Decrease) in Stockholders' Equity
Net income attributable to Brookline Bancorp, Inc.	87,717	87,717			87,717
Net income attributable to noncontrolling interest in subsidiary	43								43
Other comprehensive income (loss)	11,743	11,743				11,743
Common stock dividends	(35,110)	(35,110)			(35,110)
Dividend distribution to owners of noncontrolling interest in subsidiary	(930)	(930)		(930)
Redemption of noncontrolling interest in subsidiary	(28,992)	(18,470)		(18,470)					(10,522)
Restricted stock awards, net of awards surrendered	1,929	1,929		80	(69)		1,918
Treasury stock, repurchase shares	(1,871)	(1,871)					(1,871)
Common stock held by ESOP committed to be released	458	458		292				166
Balance end of period at Dec. 31, 2019	$ 945,606	$ 945,606	$ 852	$ 736,601	$ 265,376	$ 2,283	$ (59,073)	$ (433)	$ 0

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Common stock dividends, per share (in dollars per share)	$ 0.44	$ 0.395	$ 0.360
Common stock held by ESOP committed to be released, shares	30,402	32,382	34,356

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income attributable to Brookline Bancorp, Inc.	$ 87,717	$ 83,062	$ 50,518
Adjustments to reconcile net income to net cash provided from operating activities:
Net income attributable to noncontrolling interest in subsidiary	43	3,489	3,101
Provision for credit losses	9,583	4,951	18,988
Origination of loans and leases held-for-sale	(15,361)	(25,370)	(27,425)
Proceeds from sales of loans and leases held-for-sale, net	19,930	26,519	32,073
Deferred income tax expense (benefit)	(2)	(5,453)	10,798
Depreciation of premises and equipment	6,861	7,382	7,232
Amortization of investment securities premiums and discounts, net	1,810	2,200	2,042
Amortization of deferred loan and lease origination costs, net	7,045	6,971	6,695
Amortization of identified intangible assets	1,663	2,080	2,089
Amortization of debt issuance costs	100	100	100
(Accretion) amortization of acquisition fair value adjustments, net	(809)	354	(1,583)
Gain on investment securities, net	(508)	(227)	(11,393)
Gain on sales of loans and leases held-for-sale	(1,709)	(1,883)	(2,644)
Loss (gain) on sales of OREO and other repossessed assets, net	108	0	(79)
Write-down of OREO and other repossessed assets	903	1,234	458
Compensation under recognition and retention plans	2,683	2,546	2,308
ESOP shares committed to be released	458	543	501
Net change in:
Cash surrender value of bank-owned life insurance	(1,030)	(1,039)	(1,041)
Equity securities held-for-trading	1,215	(5,371)	0
Other assets	(63,235)	(10,855)	(2,413)
Accrued expenses and other liabilities	45,254	31,796	(5,378)
Net cash provided from operating activities	102,719	123,029	84,947
Cash flows from investing activities:
Proceeds from sales of investment securities available-for-sale	0	22,210	0
Proceeds from maturities, calls, and principal repayments of investment securities available-for-sale	68,165	82,896	71,611
Purchases of investment securities available-for-sale	(50,400)	(73,852)	(90,971)
Proceeds from maturities, calls, and principal repayments of investment securities held to maturity	28,858	3,290	3,817
Purchases of investment securities held-to-maturity	(1,430)	(8,915)	(26,873)
Proceeds from redemption/sales of restricted equity securities	20,857	12,110	24,462
Purchase of restricted equity securities	(12,924)	(13,262)	(7,927)
Proceeds from sales of loans and leases held-for-investment, net	13,860	7,294	28,608
Net increase in loans and leases	(467,493)	(593,968)	(378,906)
Acquisitions, net of cash and cash equivalents acquired	0	(24,659)	0
Purchase of premises and equipment, net	(4,997)	(3,352)	(11,557)
Proceeds from sales of OREO and other repossessed assets	6,482	2,186	3,762
Net cash used for investing activities	(399,022)	(588,022)	(383,974)
Cash flows from financing activities:
Increase in demand checking, NOW, savings and money market accounts	143,551	1,006	93,819
Increase (decrease) in certificates of deposit	232,911	580,878	166,448
Proceeds from FHLBB advances	4,029,662	6,607,745	4,685,706
Repayment of FHLBB advances	(4,055,568)	(6,713,279)	(4,705,543)
Increase (decrease) in other borrowed funds, net	7,955	5,095	(2,568)
(Decrease) increase in mortgagors' escrow accounts, net	(194)	(260)	41
Proceeds from exercise of stock options	0	490	1,469
Repurchases of common stock	(1,871)	(10,000)	0
Proceeds from issuance of common stock	0	0	81,943
Common stock issued for acquisition	0	55,182	0
Payment of dividends on common stock	(35,110)	(31,441)	(27,035)
Payment of income taxes for shares withheld in share based activity	(46)	(81)	(352)
Redemption of noncontrolling interest in subsidiary	(35,851)	0	0
Proceeds from issuance of noncontrolling units	0	130	118
Payment of dividends to owners of noncontrolling interest in subsidiary	(930)	(1,893)	(1,671)
Net cash provided from financing activities	284,509	493,572	292,375
Net (decrease) increase in cash and cash equivalents	(11,794)	28,579	(6,652)
Cash and cash equivalents at beginning of year	89,584	61,005	67,657
Cash and cash equivalents at end of year	77,790	89,584	61,005
Cash paid during the year for:
Interest on deposits, borrowed funds and subordinated debt	94,533	65,182	40,785
Income taxes	27,345	21,129	34,026
Non-cash investing activities:
Transfer from loans and leases to loan and leases held-for-sale	0	0	7,500
Transfer from loans to other real estate owned	6,105	3,020	7,161
First Commons Bank
Non-cash investing activities:
Fair value of assets acquired, net of cash and cash equivalents acquired	0	292,025	0
Fair value of liabilities assumed	$ 0	$ 278,988	$ 0

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Acquisitions	Acquisitions Eastern Funding, LLC Redemption of Non-Controlling Interest On January 4, 2019, Brookline Bank, a wholly-owned subsidiary of the Company, completed the redemption of the remaining 15.93 percent interest in Eastern Funding, LLC, a subsidiary of Brookline Bank. Brookline Bank paid $35.9 million in cash consideration for the outstanding interest in Eastern Funding, LLC. Eastern Funding, LLC is now a wholly-owned subsidiary of Brookline Bank.

Basis of Presentation

Basis of Presentation	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Overview Brookline Bancorp, Inc. (the "Company") is a bank holding company (within the meaning of the Bank Holding Company Act of 1956, as amended) and the parent of Brookline Bank, a Massachusetts-chartered trust company and Bank Rhode Island ("BankRI"), a Rhode Island-chartered financial institution (collectively referred to as the "Banks"). The Banks are all members of the Federal Reserve System. The Company is also the parent of Brookline Securities Corp. ("BSC"). The Company's primary business is to provide commercial, business and retail banking services to its corporate, municipal and retail customers through the Banks and its non-bank subsidiaries. Until February 14, 2020 (the "Merger Closing Date"), the Company was also the parent of First Ipswich Bank ("First Ipswich"), a Massachusetts-chartered trust company. Effective upon the Merger Closing Date, First Ipswich was merged with and into Brookline Bank, with Brookline as the surviving institution. Brookline Bank, which includes its wholly-owned subsidiaries BBS Investment Corp., Longwood Securities Corp., Eastern Funding LLC ("Eastern Funding"), First Ipswich Insurance Agency and First Ipswich Securities II Corp., operates 31 full-service banking offices in the greater Boston metropolitan area with two additional lending offices. BankRI, which includes its wholly-owned subsidiaries, Acorn Insurance Agency, BRI Realty Corp., Macrolease Corporation ("Macrolease"), BRI Investment Corp. and its wholly-owned subsidiary, BRI MSC Corp., operates 20 full-service banking offices in the greater Providence, Rhode Island area. The Company's activities include acceptance of commercial, municipal and retail deposits, origination of mortgage loans on commercial and residential real estate located principally in all New England states, origination of commercial loans and leases to small- and mid-sized businesses, investment in debt and equity securities, and the offering of cash management and investment advisory services. The Company also provides specialty equipment financing through its subsidiaries Eastern Funding, which is based in New York City, New York, and Macrolease, which is based in Plainview, New York. The Company and the Banks are supervised, examined and regulated by the Board of Governors of the Federal Reserve System ("FRB"). As a Massachusetts-chartered trust company, Brookline Bank is also subject to regulation under the laws of the Commonwealth of Massachusetts and the jurisdiction of the Massachusetts Division of Banks. As a Rhode Island-chartered financial institution, BankRI is subject to regulation under the laws of the State of Rhode Island and the jurisdiction of the Banking Division of the Rhode Island Department of Business Regulation. The Federal Deposit Insurance Corporation ("FDIC") offers insurance coverage on all deposits up to $250,000 per depositor at each of the Banks. As FDIC-insured depository institutions, the Banks are also secondarily subject to supervision, examination and regulation by the FDIC. Until July 31, 2019, Brookline Bank was a member bank of the Depositors Insurance Fund (the “DIF”), a private, industry-sponsored insurance fund that insures all deposits above FDIC limits for Massachusetts-chartered savings banks. Brookline Bank converted its charter from a Massachusetts-chartered savings bank to a Massachusetts-chartered trust company and ended its membership in the DIF on July 31, 2019. Excess deposits that are insured by the DIF on July 31, 2019 will continue to be insured by the DIF until July 31, 2020. Term deposits in excess of the FDIC insurance coverage will continue to be insured by the DIF until they reach maturity. Basis of Financial Statement Presentation The Company's consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles ("GAAP") as set forth by the Financial Accounting Standards Board ("FASB") in its Accounting Standards Codification and through the rules and interpretive releases of the Securities and Exchange Commission ("SEC") under the authority of federal securities laws. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances are eliminated in consolidation. In preparing these consolidated financial statements, management is required to make significant estimates and assumptions that affect the reported amounts of assets, liabilities, income, expenses and disclosure of contingent assets and liabilities. Actual results could differ from those estimates based upon changing conditions, including economic conditions and future events. Material estimates that are particularly susceptible to significant changes in the near-term include the determination of the allowance for loan and lease losses, the determination of fair market values of assets and liabilities, including acquired loans, the review of goodwill and intangibles for impairment and the review of deferred tax assets for valuation allowance. The judgments used by management in applying these significant estimates may be affected by a further and prolonged deterioration in the economic environment, which may result in changes to future financial results. For example, subsequent evaluations of the loan and lease portfolio, in light of the factors then prevailing, may result in significant changes in the allowance for loan and lease losses in future periods, and the inability to collect outstanding principal may result in increased loan and lease losses. Reclassification Certain previously reported amounts have been reclassified to conform to the current year's presentation. Cash and Cash Equivalents For purposes of reporting asset balances and cash flows, cash and cash equivalents includes cash on hand and due from banks (including cash items in process of clearing), interest-bearing deposits with banks, federal funds sold, money market mutual funds and other short-term investments with original maturities of three months or less. Investment Securities Investment securities, other than those reported as short-term investments, are classified at the time of purchase as "available-for-sale," "held-to-maturity," or "held-for-trading." Classification is periodically re-evaluated for consistency with the Company's goals and objectives. Equity investments in the Federal Home Loan Bank of Boston ("FHLBB"), the Federal Reserve Bank of Boston and other restricted equities are discussed in more detail in Note 5, "Restricted Equity Securities." Investment Securities Available-for-Sale, Held-to-Maturity, and Held-for-Trading Investment securities for which the Company has the positive intent and ability to hold to maturity are classified as held-to-maturity and carried at amortized cost. Those investment securities held for indefinite periods of time but not necessarily to maturity are classified as available-for-sale. Investment securities held for indefinite periods of time include investment securities that management intends to use as part of its asset/liability, liquidity, and/or capital management strategies and may be sold in response to changes in interest rates, maturities, asset/liability mix, liquidity needs, regulatory capital needs or other business factors. Investment securities available-for-sale are carried at estimated fair value, primarily obtained from a third-party pricing service, with unrealized gains and losses reported on an after-tax basis in stockholders' equity as accumulated other comprehensive income or loss. Investment securities expected to be held for very short term duration, used for hedging, or are marketable equity securities are typically designated held-for-trading. Held-for-trading securities are carried at estimated fair value principally based on market prices and dealer quotes received from third-party and nationally-recognized pricing services. Gains and losses for held-for-trading are reported on the income statement as gains on investment securities, net. As of December 31, 2019 and 2018 , the Company did not make any adjustments to the prices provided by the third-party pricing service. Security transactions are recorded on the trade date. Realized gains and losses are determined using the specific identification method and are recorded in non-interest income. Interest and dividends on securities are recorded using the accrual method. Premiums and discounts on securities are amortized or accreted into interest income using the level-yield method over the remaining period to contractual maturity, adjusted for the effect of actual prepayments in the case of mortgage-backed securities ("MBSs") and collateralized mortgage obligations ("CMOs"). These estimates of prepayment assumptions are made based upon the actual performance of the underlying security, current interest rates, the general market consensus regarding changes in mortgage interest rates, the contractual repayment terms of the underlying loans, the priority rights of the investors to the cash flows from the mortgage securities and other economic conditions. When differences arise between anticipated prepayments and actual prepayments, the effective yield is recalculated to reflect actual payments to date and anticipated future payments. Unamortized premium or discount is adjusted to the amount that would have existed had the new effective yield been applied since purchase, with a corresponding charge or credit to interest income. Management evaluates securities for other-than-temporary impairment ("OTTI") on a periodic basis. Factors considered in determining whether an impairment is OTTI include: (1) the length of time and the extent to which the fair value has been less than amortized cost, (2) projected future cash flows, (3) the financial condition and near-term prospects of the issuers, and (4) the intent and ability of the Company to hold the investment for a period of time sufficient to allow for any anticipated recovery in fair value. The Company records an OTTI loss in an amount equal to the entire difference between the fair value and amortized cost if: (1) the Company intends to sell an impaired investment security, (2) it is more likely than not that the Company will be required to sell the investment security before its amortized cost, or (3) for debt securities, the present value of expected future cash flows is not sufficient to recover the entire amortized cost basis. If an investment security is determined to be OTTI but the Company does not intend to sell the investment security, only the credit portion of the estimated loss is recognized in earnings, with the non credit portion of the loss recognized in other comprehensive income. Restricted Equity Securities The Company invests in the stock of the FHLBB, the Federal Reserve Bank of Boston and a small amount of other restricted securities. No ready market exists for these stocks, and they have no quoted market values. The Banks, as members of the FHLBB, are required to maintain investments in the capital stock of the FHLBB equal to their membership base investments plus an activity-based investment determined according to the Banks' level of outstanding FHLBB advances. Federal Reserve Bank of Boston stock was purchased and is redeemable at par. The Company reviews for impairment of these securities based on the ultimate recoverability of the cost basis in the stock. As of December 31, 2019 and 2018 , no impairment has been recognized. Loans Originated Loans Loans the Company originates for the portfolio, and for which it has the intent and ability to hold to maturity, are reported at amortized cost, inclusive of deferred loan origination fees and expenses, less unadvanced funds due borrowers on loans and the allowance for loan and lease losses. Interest income on loans and leases originated for the portfolio is accrued on unpaid principal balances as earned. Loan origination fees and direct loan origination costs are deferred, and the net fee or cost is recognized in interest income using the interest method. Deferred amounts are recognized for fixed-rate loans over the contractual life of the loans and for adjustable-rate loans over the period of time required to adjust the contractual interest rate to a yield approximating a market rate at the origination date. If a loan is prepaid, the unamortized portion of the loan origination costs, including third party referral related costs not subject to rebate from the dealer, is charged to income. Loans and Leases Held-for-Sale Management identifies and designates certain newly originated loans and leases for sale to specific financial institutions, subject to the underwriting criteria of those financial institutions. These loans and leases are held for sale and are carried at the lower of cost or market as determined in the aggregate. Deferred loan fees and costs are included in the determination of the gain or loss on sale. Acquired Loans Acquired loans that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments receivable are initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance. The difference between the undiscounted cash flows expected at acquisition and the recorded fair value of the loan, or the “accretable yield,” is recognized as interest income on a level-yield method over the life of the loan. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “nonaccretable difference,” are not recognized as a yield adjustment or as a loss accrual or a valuation allowance. The Company uses a model to reforecast expected cash flows on these acquired loans. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows are recognized as impairment. Valuation allowances on these impaired loans reflect only losses incurred after the acquisition (meaning the present value of all cash flows expected at acquisition that ultimately are not to be received). For the First Commons Bank portfolio, minimal loss is expected from the loan portfolio based on historical performance, management’s due diligence, and market conditions. Therefore, the fair value of the loan portfolio was calculated on an individual loan basis using a discounted cash flow analysis factoring in the contractual terms of the loans, current market pricing, and prepayment expectations. Nonperforming Loans Nonaccrual Loans Accrual of interest on loans generally is discontinued when contractual payment of principal or interest becomes past due 90 days or, if in management's judgment, reasonable doubt exists as to the full timely collection of interest. Exceptions may be made if the loan has matured and is in the process of renewal or is well-secured and in the process of collection. When a loan is placed on nonaccrual status, interest accruals cease and uncollected accrued interest is reversed and charged against current interest income. Interest payments on nonaccrual loans are generally applied to principal. If collection of the principal is reasonably assured, interest payments are recognized as income on the cash basis. Loans are generally returned to accrual status when principal and interest payments are current, full collectability of principal and interest is reasonably assured and a consistent record of at least six consecutive months of performance has been achieved. Impaired Loans A loan is considered to be impaired when, based on current information and events, it is probable that the Company will be unable to collect all amounts due (both interest and principal) according to the contractual terms of the loan agreement. Smaller-balance, homogeneous loans that are evaluated collectively for impairment, such as residential, home equity and other consumer loans are specifically excluded from the impaired loan portfolio except where the loan is classified as a troubled debt restructuring. The Company has defined the population of impaired loans to include nonaccrual loans and troubled debt restructured ("TDR") loans. When the ultimate collectability of the total principal of an impaired loan or lease is in doubt and the loan is on nonaccrual status, all payments are applied to principal, under the cost recovery method. When the ultimate collectability of the total principal of an impaired loan or lease is not in doubt and the loan or lease is on nonaccrual status, contractual interest is credited to interest income when received, under the cash basis method. The value of an impaired loan is measured based upon the present value of expected future cash flows discounted at the loan's effective interest rate, or the fair value of the collateral if the loan is collateral-dependent and its payment is expected solely based on the underlying collateral. For impaired loans deemed collateral dependent, where impairment is measured using the fair value of the collateral, the Company will either obtain a new appraisal or use another available source of collateral assessment to determine a reasonable estimate of the fair value of the collateral. Interest collected on impaired loans is either applied against principal or reported as income according to management's judgment as to the collectability of principal. If management does not consider a loan ultimately collectible within an acceptable time frame, payments are applied as principal to reduce the loan balance. If full collection of the remaining recorded investment should subsequently occur, interest receipts are recorded as interest income on a cash basis. Troubled Debt Restructured Loans In cases where a borrower experiences financial difficulties and the Company makes certain concessionary modifications to contractual terms, the loan is classified as a TDR loan. In determining whether a debtor is experiencing financial difficulties, the Company considers, among other factors, whether the debtor is in payment default or is likely to be in payment default in the foreseeable future without the modification, if the debtor declared or is in the process of declaring bankruptcy, there is substantial doubt that the debtor will continue as a going concern, the debtor's entity-specific projected cash flows will not be sufficient to service its debt, or the debtor cannot obtain funds from sources other than the existing creditors at market terms for debt with similar risk characteristics. Large groups of small-balance homogeneous loans such as residential real estate, residential construction, home equity and other consumer portfolios are collectively evaluated for impairment. As such, the Company does not typically identify individual loans within these groupings as impaired loans or for impairment evaluation and disclosure. However, the Company evaluates all TDRs for impairment on an individual loan basis regardless of loan type. Modifications may include interest-rate reductions, short-term (defined as one year or less) changes in payment structure to interest-only payments, short-term extensions of the loan's original contractual term, or less frequently, principal forgiveness, interest capitalization, forbearance and other actions intended to minimize economic loss and avoid foreclosure or repossession of collateral. Typically, TDRs are placed on nonaccrual status and reported as nonperforming loans. Generally, a nonaccrual loan that is restructured remains on nonaccrual for a period of six months to demonstrate that the borrower can meet the restructured terms; however, performance prior to the restructuring, or significant events that coincide with the restructuring, are considered in assessing whether the borrower can meet the new terms and may result in the loan being returned to accrual status at the time of restructuring or after a shorter performance period. If the borrower's ability to meet the revised payment schedule is not reasonably assured, the loan remains classified as a nonaccrual loan. Loans restructured at an interest rate equal to or greater than that of a new loan with comparable risk at the time the loan agreement is modified may be excluded from restructured loan disclosures in years subsequent to the restructuring if they are in compliance with the modified terms. Allowance for Loan and Lease Losses Management has established a methodology to determine the adequacy of the allowance for loan and lease losses that assesses the risks and losses inherent in the loan and lease portfolio. Additions to the allowance for loan and lease losses are made by charges to the provision for credit losses. Losses on loans and leases are charged off against the allowance when all or a portion of a loan or lease is considered uncollectible. Subsequent recoveries on loans previously charged off, if any, are credited to the allowance when realized. Management uses a consistent and systematic process and methodology to evaluate the adequacy of the allowance for loan and lease losses on a quarterly basis. For purposes of determining the allowance for loan and lease losses, the Company has segmented certain loans and leases in the portfolio by product type into the following segments: (1) commercial real estate loans, (2) commercial loans and leases, (3) and consumer loans. Portfolio segments are further disaggregated into classes based on the associated risks within the segments. Commercial real estate loans are divided into three classes: commercial real estate mortgage loans, multi-family mortgage loans, and construction loans. Commercial loans and leases are divided into three classes: commercial loans which includes taxi medallion loans, equipment financing, and loans to condominium associations. Consumer loans are divided into three classes: residential mortgage loans, home equity loans, and other consumer loans. A formula-based credit evaluation approach is applied to each group, coupled with an analysis of certain loans for impairment. The general allowance related to loans collectively evaluated for impairment is determined using a formula-based approach utilizing the risk ratings of individual credits and loss factors derived from historic portfolio loss rates over a lookback period, which include estimates of incurred losses over an estimated loss emergence period (“LEP”). The LEP was generated utilizing a charge-off look-back analysis which studied the time from the first indication of elevated risk of repayment (or other early event indicating a problem) to eventual charge-off to support the LEP considered in the allowance calculation. This reserving methodology established the approximate number of months of LEP that represents incurred losses for each portfolio. In addition to quantitative measures, relevant qualitative factors include, but are not limited to: (1) levels and trends in past due and impaired loans, (2) levels and trends in charge-offs, (3) changes in underwriting standards, policy exceptions, and credit policy, (4) experience of lending management and staff, (5) economic trends, (6) industry conditions, (7) effects of changes in credit concentrations, (8) interest rate environment, and (9) regulatory and other changes. The general allowance related to the acquired loans collectively evaluated for impairment is determined based upon the degree, if any, of deterioration in the pooled loans subsequent to acquisition. The qualitative factors used in the determination are the same as those used for originated loans. During 2015, the Company enhanced and refined its general allowance methodology. Under the enhanced methodology, management combined the historical loss histories of the Banks to generate a single set of historical loss ratios. Management believes it is appropriate to aggregate the ratios as the Banks share common environmental factors, operate in similar geographic markets, and utilize common underwriting standards in accordance with the Company's Credit Policy. In prior periods, a historical loss history applicable to each Bank was used. Management employed a similar analysis for the consolidation of the qualitative factors as it did for the quantitative factors. Again, management believes the realignment of the existing nine qualitative factors used at each of the Banks into a single group of factors used for the Company is appropriate based on the commonality of environmental factors, markets and underwriting standards among the Banks. Prior to 2015, each of the Banks utilized a set of qualitative factors applicable to each Bank. The Company’s December 31, 2019 allowance calculation included a further segmentation of the commercial loans and leases to reflect the increased risk in the Company’s taxi medallion portfolio. As of December 31, 2019 , this portfolio is approximately $10.3 million . Based on industry conditions, management established a loss factor for this portfolio that best represents the changing risks associated with it. Based on the refinements to the Company’s allowance methodology discussed above, management determined that the potential risks anticipated by the unallocated allowance are now incorporated into the allowance methodology, making the unallocated allowance unnecessary. Prior to 2015, the unallocated allowance was used to recognize the estimated risk associated with the allocated general and specific allowances. It incorporated management’s evaluation of existing conditions that were not included in the allocated allowance determinations and provided for losses that arise outside of the ordinary course of business. Specific valuation allowances are established for impaired originated loans with book values greater than the discounted present value of expected future cash flows or, in the case of collateral-dependent impaired loans, for any excess of a loan's book balance and the fair value of its underlying collateral. Specific valuation allowances are established for acquired loans with deterioration in the discounted present value of expected future cash flows since acquisitions or, in the case of collateral dependent impaired loans, for any increase in the excess of a loan's book balance greater than the fair value of its underlying collateral. A specific valuation allowance for losses on TDR loans is determined by comparing the net carrying amount of the troubled debt restructured loan with the restructured loan's cash flows discounted at the original effective rate. Impaired loans are reviewed quarterly with adjustments made to the calculated reserve as necessary. As of December 31, 2019 , management believes that the methodology for calculating the allowance is sound and that the allowance provides a reasonable basis for determining and reporting on probable losses in the Company’s loan portfolios. Liability for Unfunded Commitments In the ordinary course of business, the Company enters into commitments to extend credit, commercial letters of credit, and standby letters of credit. Such financial instruments are recorded in the financial statements when they become payable. The credit risk associated with these commitments is evaluated in a manner similar to the allowance for loan losses. Premises and Equipment Premises and equipment are carried at cost less accumulated depreciation and amortization, except for land which is carried at cost. Premises and equipment are depreciated using the straight-line method over the estimated useful life of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful life of the improvements. Costs related to internal-use software development projects that provide significant new functionality are capitalized. Internal-use software is software acquired or modified solely to meet the Company's needs and for which there is no plan to market the software externally. Direct and indirect costs associated with the application development stage of internal use software are capitalized until such time that the software is substantially complete and ready for its intended use. Capitalized costs are amortized on a straight-line basis over the remaining estimated life of the software. Computer software and development costs incurred in the preliminary project stage, as well as training and maintenance costs, are expensed as incurred. Leases The Company leases certain office space under various noncancellable operating leases as well as certain other assets. These leases have original terms ranging from 3 years to over 25 years . Certain leases contain renewal options and escalation clauses which can increase rental expenses based principally on the consumer price index and fair market rental value provisions. All of the Company's current outstanding leases are classified as operating leases. Bank-Owned Life Insurance The Company acquired bank-owned life insurance ("BOLI") plans as part of its acquisitions of First Ipswich and BankRI. BOLI represents life insurance on the lives of certain current and former employees who have provided positive consent allowing their employer to be the beneficiary of such policies. BankRI and Brookline Bank are the beneficiaries of their respective policies. BankRI and Brookline Bank utilize BOLI as tax-efficient financing for their benefit obligations to their employees, including their retirement obligations and Supplemental Executive Retirement Plans ("SERPs"). Since BankRI and Brookline Bank are the primary beneficiaries of their respective insurance policies, increases in the cash value of the policies, as well as insurance proceeds received, are recorded in non-interest income and are not subject to income taxes. BOLI is recorded at the cash value of the policies, less any applicable cash surrender charges, and is reflected as an asset in the accompanying consolidated balance sheets. Cash proceeds, if any, are classified as cash flows from investing activities. The Company reviews the financial strength of the insurance carriers prior to the purchase of BOLI to ensure minimum credit ratings of at least investment grade. The financial strength of the carriers is reviewed at least annually, and BOLI with any individual carrier is limited to 10% of the Company's capital. Total BOLI is limited to 25% of the Company's capital. Goodwill and Other Identified Intangible Assets Goodwill represents the excess of the cost of an acquisition over the fair value of the net assets acquired. Goodwill and indefinite-lived identified intangible assets are not subject to amortization. Definite-lived identified intangible assets are assets resulting from acquisitions that are being amortized over their estimated useful lives. The recoverability of goodwill and identified intangible assets is evaluated for impairment at least annually. As part of this evaluation, the Company makes a qualitative assessment of whether it is more likely than not that the fair value of an acquired asset is greater than its carrying amount. If the Company qualitatively concludes that it is more likely than not that the fair value of an acquired asset is greater than its carrying amount, no further testing is necessary. If, however, the Company qualitatively concludes that the fair value of an acquired asset is less than its carrying value, the Company should recognize an impairment charge for the amount by which the carrying amount exceeds the fair value. The Company did not have any impairment of Goodwill and other identified intangible assets as of December 31, 2019 and 2018 . OREO and Other Repossessed Assets OREO and other repossessed assets consists of properties acquired through foreclosure, real estate acquired through acceptance of a deed in lieu of foreclosure and loans determined to be substantively repossessed. Real estate loans that are substantively repossessed include only those loans for which the Company has taken possession of the collateral. OREO and other repossessed assets which consist of vehicles and equipment, if any, are recorded initially at estimated fair value less costs to sell, resulting in a new cost basis. The amount by which the recorded investment in the loan exceeds the fair value (net of estimated cost to sell) of the foreclosed or repossessed asset is charged to the allowance for loan and lease losses. Such evaluations are based on an analys

Cash, Cash Equivalents and Shor

Cash, Cash Equivalents and Short-Term Investments	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Short-Term Investments	Cash, Cash Equivalents and Short-Term Investments The Banks are required to maintain average reserve balances with the FRB based upon a percentage of certain of the Banks' deposits. As of December 31, 2019 and 2018 , the average amount required to be held before a credit for vault cash was $10.5 million and $8.2 million , respectively. Aggregate reserve balances included in cash and cash equivalents were $53.0 million and $48.0 million , respectively, as of December 31, 2019 and 2018 . Short-term investments are summarized as follows: At December 31, 2019 2018 (In Thousands) FRB interest bearing reserve $ 39,964 $ 34,914 FHLB overnight deposits 4,237 4,628 Federal funds sold — 2,500 Total short-term investments $ 44,201 $ 42,042

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Investment Securities	Investment Securities The following tables set forth investment securities available-for-sale, held-to-maturity and equity securities held-for-trading at the dates indicated: At December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In Thousands) Investment securities available-for-sale: GSE debentures $ 182,922 $ 2,939 $ 58 $ 185,803 GSE CMOs 87,001 22 1,091 85,932 GSE MBSs 153,049 797 503 153,343 SBA commercial loan asset-backed securities 34 — — 34 Corporate debt obligations 28,484 502 — 28,986 U.S. treasury bonds 44,675 338 116 44,897 Total investment securities available-for-sale $ 496,165 $ 4,598 $ 1,768 $ 498,995 Investment securities held-to-maturity: GSE debentures $ 31,228 $ 113 $ 51 $ 31,290 GSEs MBSs 9,360 — 81 9,279 Municipal obligations 45,692 822 — 46,514 Foreign government obligations 500 — 22 478 Total investment securities held-to-maturity $ 86,780 $ 935 $ 154 $ 87,561 Equity securities held-for-trading $ 561 $ 3,581 At December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In Thousands) Investment securities available-for-sale: GSE debentures $ 184,072 $ 99 $ 3,092 $ 181,079 GSE CMOs 107,363 17 4,250 103,130 GSE MBSs 169,334 124 4,369 165,089 SBA commercial loan asset-backed securities 51 — — 51 Corporate debt obligations 40,618 — 910 39,708 U.S. treasury bonds 13,812 65 141 13,736 Total investment securities available-for-sale $ 515,250 $ 305 $ 12,762 $ 502,793 Investment securities held-to-maturity: GSE debentures $ 50,546 $ 22 $ 967 $ 49,601 GSEs MBSs 11,426 — 295 11,131 Municipal obligations 52,304 10 716 51,598 Foreign government obligations 500 — — 500 Total investment securities held-to-maturity $ 114,776 $ 32 $ 1,978 $ 112,830 Equity securities held for trading 1,170 $ 4,207 As of December 31, 2019 , the fair value of all investment securities available-for-sale was $499.0 million , with net unrealized gains of $2.8 million , compared to a fair value of $502.8 million and net unrealized losses of $12.5 million as of December 31, 2018 . As of December 31, 2019 , $205.6 million , or 41.2% of the portfolio, had gross unrealized losses of $1.8 million , compared to $ 466.7 million , or 92.8% of the portfolio, with gross unrealized losses of $12.8 million as of December 31, 2018 . As of December 31, 2019 , the fair value of all investment securities held-to-maturity was $87.6 million , with net unrealized gains of $0.8 million , compared to a fair value of $112.8 million with net unrealized losses of $1.9 million as of December 31, 2018 . As of December 31, 2019 , $22.3 million , or 25.5% of the portfolio, had gross unrealized losses of $0.2 million . As of December 31, 2018 , $102.1 million , or 90.5% of the portfolio had gross unrealized losses of $2.0 million . As of December 31, 2019 , the Company reported a fair value of $3.6 million of equity securities held-for-trading. As of December 31, 2018 , the Company reported a fair value of $4.2 million of equity securities held-for-trading. Investment Securities as Collateral As of December 31, 2019 and 2018 , respectively, $433.6 million and $442.5 million of investment securities were pledged as collateral for repurchase agreements; municipal deposits; treasury, tax and loan deposits ("TT&L"); swap agreements; and FHLBB borrowings. The Banks did not have any outstanding FRB borrowings as of December 31, 2019 and 2018 . Other-Than-Temporary Impairment ("OTTI") Investment securities as of December 31, 2019 and 2018 that have been in a continuous unrealized loss position for less than twelve months or twelve months or longer are as follows: At December 31, 2019 Less than Twelve Months Twelve Months or Longer Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (In Thousands) Investment securities available-for-sale: GSE debentures $ 10,965 $ 58 $ — $ — $ 10,965 $ 58 GSE CMOs 28,659 217 55,885 874 84,544 1,091 GSE MBSs 42,046 115 42,257 388 84,303 503 SBA commercial loan asset-backed securities — — 33 — 33 — U.S. Treasury bonds 25,754 116 — — 25,754 116 Temporarily impaired investment securities available-for-sale 107,424 506 98,175 1,262 205,599 1,768 Investment securities held-to-maturity: GSE debentures 8,714 30 2,977 21 11,691 51 GSEs MBSs — — 9,257 81 9,257 81 Municipal obligations 710 — 205 — 915 — Foreign government obligations 478 22 — — 478 22 Temporarily impaired investment securities held-to-maturity 9,902 52 12,439 102 22,341 154 Total temporarily impaired investment securities $ 117,326 $ 558 $ 110,614 $ 1,364 $ 227,940 $ 1,922 At December 31, 2018 Less than Twelve Months Twelve Months or Longer Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (In Thousands) Investment securities available-for-sale: GSE debentures $ 25,780 $ 191 $ 130,284 $ 2,901 $ 156,064 $ 3,092 GSE CMOs — — 102,630 4,250 102,630 4,250 GSE MBSs 21,487 113 138,051 4,256 159,538 4,369 SBA commercial loan asset-backed securities — — 51 — 51 — Corporate debt obligations 10,019 93 29,689 817 39,708 910 U.S. Treasury bonds 3,927 37 4,753 104 8,680 141 Temporarily impaired investment securities available-for-sale 61,213 434 405,458 12,328 466,671 12,762 Investment securities held-to-maturity: GSE debentures — — 40,653 967 40,653 967 GSEs MBSs — — 11,080 295 11,080 295 Municipal obligations 14,813 107 35,058 609 49,871 716 Foreign government obligations — — 500 — 500 — Temporarily impaired investment securities held-to-maturity 14,813 107 87,291 1,871 102,104 1,978 Total temporarily impaired investment securities $ 76,026 $ 541 $ 492,749 $ 14,199 $ 568,775 $ 14,740 The Company performs regular analysis on the investment securities available-for-sale portfolio to determine whether a decline in fair value indicates that an investment security is OTTI. In making these OTTI determinations, management considers, among other factors, the length of time and extent to which the fair value has been less than amortized cost; projected future cash flows; credit subordination and the creditworthiness; capital adequacy and near-term prospects of the issuers. Management also considers the Company's capital adequacy, interest-rate risk, liquidity and business plans in assessing whether it is more likely than not that the Company will sell or be required to sell the investment securities before recovery. If the Company determines that a decline in fair value is OTTI and that it is more likely than not that the Company will not sell or be required to sell the investment security before recovery of its amortized cost, the credit portion of the impairment loss is recognized in the Company's consolidated statement of income and the noncredit portion is recognized in accumulated other comprehensive income. The credit portion of the OTTI impairment represents the difference between the amortized cost and the present value of the expected future cash flows of the investment security. If the Company determines that a decline in fair value is OTTI and it is more likely than not that it will sell or be required to sell the investment security before recovery of its amortized cost, the entire difference between the amortized cost and the fair value of the security will be recognized in the Company's consolidated statement of income. Investment Securities Available-For-Sale Impairment Analysis The following discussion summarizes, by investment security type, the basis for evaluating if the applicable investment securities within the Company’s available-for-sale portfolio were OTTI as of December 31, 2019 . Based on the analysis below and the determination that, it is more likely than not that the Company will not sell or be required to sell the investment securities before recovery of its amortized cost. The Company's ability and intent to hold these investment securities until recovery is supported by the Company's strong capital and liquidity positions as well as its historically low portfolio turnover. As such, management has determined that the investment securities are not OTTI as of December 31, 2019 . If market conditions for investment securities worsen or the creditworthiness of the underlying issuers deteriorates, it is possible that the Company may recognize additional OTTI in future periods. U.S. Government-Sponsored Enterprises The Company invests in securities issued by U.S. Government-sponsored enterprises ("GSEs"), including GSE debentures, mortgage-backed securities ("MBSs"), and collateralized mortgage obligations ("CMOs"). GSE securities include obligations issued by the Federal National Mortgage Association ("FNMA"), the Federal Home Loan Mortgage Corporation ("FHLMC"), the Government National Mortgage Association ("GNMA"), the Federal Home Loan Banks ("FHLB") and the Federal Farm Credit Bank. As of December 31, 2019 , only GNMA MBSs and CMOs, and Small Business Administration ("SBA") commercial loan asset-backed securities in our available-for-sale portfolio with an estimated fair value of $17.4 million were backed explicitly by the full faith and credit of the U.S. Government, compared to $20.6 million as of December 31, 2018 . As of December 31, 2019 , the Company owned 60 GSE debentures with a total fair value of $185.8 million , and a net unrealized gain of $2.9 million . As of December 31, 2018 , the Company held 60 GSE debentures with a total fair value of $181.1 million , and a net unrealized loss of $3.0 million . As of December 31, 2019 , 5 of the 60 securities in this portfolio were in an unrealized loss position. As of December 31, 2018 , 51 of the 60 securities in this portfolio were in an unrealized loss position. All securities are performing and backed by the implicit (FHLB/FNMA/FHLMC) or explicit (GNMA/SBA) guarantee of the U.S. Government. For the year ended December 31, 2019 , the Company did no t purchase any GSE debentures, compared to the year ended December 31, 2018 , when the Company purchased a total of $33.9 million of GSE debentures. As of December 31, 2019 , the Company owned 61 GSE CMOs with a total fair value of $85.9 million and a net unrealized loss of $1.1 million . As of December 31, 2018 , the Company held 61 GSE CMOs with a total fair value of $103.1 million with a net unrealized loss of $4.2 million . As of December 31, 2019 , 45 of the 61 securities in this portfolio were in an unrealized loss position. As of December 31, 2018 , 46 of the 61 securities in this portfolio were in an unrealized loss position. All securities are performing and backed by the implicit (FHLB/FNMA/FHLMC) or explicit (GNMA) guarantee of the U.S Government. For the years ended December 31, 2019 and 2018 , the Company did no t purchase any GSE CMOs. As of December 31, 2019 , the Company owned 150 GSE MBSs with a total fair value of $153.3 million and a net unrealized gain of $0.3 million . As of December 31, 2018 , the Company held 162 GSE MBSs with a total fair value of $165.1 million with a net unrealized loss of $4.2 million . As of December 31, 2019 , 48 of the 150 securities in this portfolio were in an unrealized loss position. As of December 31, 2018 , 93 of the 162 securities in this portfolio were in an unrealized loss position. All securities are performing and backed by the implicit (FHLB/FNMA/FHLMC) or explicit (GNMA) guarantee of the U.S Government. For the years ended December 31, 2019 and 2018 , the Company purchased a total of $19.6 million and $15.2 million , respectively, of GSE MBSs. SBA Commercial Loan Asset-Backed As of December 31, 2019 , the Company owned 4 SBA securities with a total fair value of $34.0 thousand , which approximated amortized cost. As of December 31, 2018 , the Company owned 4 SBA securities with a total fair value of $51.0 thousand which approximated amortized cost. As of December 31, 2019 , 3 of the 4 securities in this portfolio were in an unrealized loss position. As of December 31, 2018 , all of the securities in this portfolio were in an unrealized loss position. All securities are performing and backed by the explicit (SBA) guarantee of the U.S Government. For the years ended December 31, 2019 and 2018 , the Company did no t purchase any SBA securities. Corporate Obligations The Company may invest in high-quality corporate obligations to provide portfolio diversification and improve the overall yield on the portfolio. As of December 31, 2019 , the Company owned 8 corporate obligation securities with a total fair value of $29.0 million and a net unrealized gain of $0.5 million . This compares to 11 corporate obligation securities with a total fair value of $39.7 million and a net unrealized loss of $0.9 million as of December 31, 2018 . As of December 31, 2019 , none of the securities in this portfolio were in an unrealized loss position. As of December 31, 2018 , all 11 of the securities in this portfolio were in an unrealized loss position. Full collection of the obligations is expected because the financial condition of the issuers is sound, they have not defaulted on scheduled payments, the obligations are rated investment grade, and the Company has the ability and intent to hold the obligations for a period of time to recover the amortized cost. For the years ended December 31, 2019 and 2018 , the Company did no t purchase any corporate obligations. U.S. Treasury Bonds The Company invests in securities issued by the U.S. government. As of December 31, 2019 , the Company owned 9 U.S. Treasury bonds with a total fair value of $44.9 million and a net unrealized gain of $0.2 million . As of December 31, 2018 , the Company owned 7 U.S. Treasury bonds with a total fair value of $13.7 million and a net unrealized loss of $0.1 million . As of December 31, 2019 , 5 of the 9 securities in this portfolio were in an unrealized loss position. As of December 31, 2018 , 2 of the 7 securities in this portfolio were in unrealized loss positions. For the years ended December 31, 2019 and 2018 , the Company purchased $30.8 million and $24.7 million in U.S. Treasury bonds, respectively. Equity Securities Held-for-Trading From time to time, the Company will invest in equity securities held-for-trading. As of December 31, 2019 and 2018 , the Company owned equity securities held-for-trading with a fair value of $3.6 million and $4.2 million , respectively. Investment Securities Held-to-Maturity Impairment Analysis The following discussion summarizes by investment security type, the basis for evaluating if the applicable investment securities within the Company's held-to-maturity portfolio were OTTI at December 31, 2019 . Management does not intend to sell these securities prior to maturity. U.S. Government-Sponsored Enterprises As of December 31, 2019 , the Company owned 10 GSE debentures with a total fair value of $31.3 million and a net unrealized gain of $0.1 million . As of December 31, 2018 , the Company owned 17 GSE debentures with a total fair value of $49.6 million and a net unrealized loss of $0.9 million . As of December 31, 2019 , 4 of the 10 securities in this portfolio were in an unrealized loss position. At December 31, 2018 , 14 of the 17 securities in this portfolio were in an unrealized loss position. All securities are performing and backed by the implicit (FHLB/FNMA/FHLMC) or explicit (GNMA) guarantee of the U.S Government. For the year ended December 31, 2019 , the Company did no t purchase any GSE debentures, compared to the year ended December 31, 2018 , when the Company purchased a total of $8.9 million of GSE debentures. As of December 31, 2019 , the Company owned 8 GSE MBSs with a total fair value of $9.3 million and a net unrealized loss of $0.1 million . As of December 31, 2018 , the Company owned 8 GSE MBSs with a total fair value of $11.1 million and an unrealized loss of $0.3 million . As of December 31, 2019 and 2018 , all securities in this portfolio were in an unrealized loss position. All securities are performing and backed by the implicit (FHLB/FNMA/FHLMC) or explicit (GNMA) guarantee of the U.S. Government. During the year ended December 31, 2019 and 2018 , the Company did no t purchase any GSE MBSs. Municipal Obligations The Company invests in certain state and municipal securities with high credit ratings for portfolio diversification and tax planning purpose. As of December 31, 2019 , the Company owned 93 municipal obligation securities with a total fair value and total amortized cost of $46.5 million and $45.7 million , respectively. As of December 31, 2018 , the Company owned 98 municipal obligation securities with a total fair value of $51.6 million and an amortized cost of $52.3 million , respectively. As of December 31, 2019 , 6 of the 93 securities in this portfolio were in an unrealized loss position as compared to December 31, 2018 , when 94 of the 98 securities were in an unrealized loss position. During the year ended December 31, 2019 , the Company purchased a total of $0.9 million of municipal obligations, compared to the year ended December 31, 2018 , when the Company did no t purchase any municipal obligations. Foreign Government Obligations As of December 31, 2019 and 2018 , the Company owned one foreign government obligation security with a fair value and amortized cost of $0.5 million . During the year ended December 31, 2019, the Company repurchased the foreign government obligation security that matured during the first quarter of 2019. As of December 31, 2019 and 2018 , the security was in an unrealized loss position. During the year ended December 31, 2019 and 2018 , the Company did no t purchase any additional foreign government obligation securities. Portfolio Maturities The final stated maturities of the debt securities are as follows for the periods indicated: At December 31, 2019 2018 Amortized Cost Estimated Fair Value Weighted Average Rate Amortized Cost Estimated Fair Value Weighted Average Rate (Dollars in Thousands) Investment securities available-for-sale: Within 1 year $ 12,797 $ 12,804 1.76% $ 12,041 $ 12,007 2.03% After 1 year through 5 years 217,569 220,757 2.19% 195,701 192,692 2.14% After 5 years through 10 years 93,805 94,212 2.04% 115,665 112,819 2.18% Over 10 years 171,994 171,222 2.12% 191,843 185,275 2.17% $ 496,165 $ 498,995 2.13% $ 515,250 $ 502,793 2.16% Investment securities held-to-maturity: Within 1 year $ 6,366 $ 6,381 1.33% $ 7,640 $ 7,618 1.17% After 1 year through 5 years 63,898 64,559 1.81% 72,735 71,492 1.84% After 5 years through 10 years 7,177 7,364 1.79% 23,025 22,640 2.20% Over 10 years 9,339 9,257 1.90% 11,376 11,080 2.13% $ 86,780 $ 87,561 1.82% $ 114,776 $ 112,830 1.89% Actual maturities of debt securities will differ from those presented above since certain obligations amortize and may also provide the issuer the right to call or prepay the obligation prior to scheduled maturity without penalty. MBSs and CMOs are included above based on their final stated maturities; the actual maturities, however, may occur earlier due to anticipated prepayments and stated amortization of cash flows. As of December 31, 2019 , issuers of debt securities with an estimated fair value of $37.6 million had the right to call or prepay the obligations. Of the $37.6 million , approximately $3.0 million matures within 1 year, $34.6 million matures in 1 - 5 years, and none mature after five years. As of December 31, 2018 , issuers of debt securities with an estimated fair value of approximately $19.1 million had the right to call or prepay the obligations. Of the $19.1 million , none of the obligations mature within 1 year, $8.4 million mature in 1-5 years, $10.7 million mature in 6-10 years, and none mature after ten years. Security Sales Security transactions are recorded on the trade date. When securities are sold, the adjusted cost of the specific security sold is used to compute the gain or loss on the sale. On March 6, 2018, the Company, through its wholly owned subsidiary, BSC, received $0.6 million in cash and 11,303 shares of Community Bank Systems, Inc. ("CBU") common stock as settlement for the indemnification escrow on the 12 month anniversary date of the merger between Northeast Retirement Securities, Inc. and CBU. The Company subsequently sold all 11,303 shares of the CBU stock and recognized a gain on the sale of $0.6 million . During the month of March 2018, the Company, through Brookline Bank’s wholly owned subsidiary, LSC, sold three trust preferred securities with a book value of $1.5 million for a loss of $0.1 million . The table below includes the activity with respect to the sale of the trust preferred securities and restricted equity securities. On December 17, 2019, the Company sold 100,000 shares of marketable equity securities, for a loss of $232 thousand . Sales of investment and restricted equity securities are summarized as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Proceeds from sales of debt securities $ — $ 20,000 $ — Proceeds from sales of marketable and restricted equity securities 1,212 2,700 11,393 Gross gains from sales — 1,472 11,612 Gross losses from sales (232 ) (68 ) (219 ) Gain on sales of securities, net $ (232 ) $ 1,404 $ 11,393

Restricted Equity Securities

Restricted Equity Securities	12 Months Ended
	Dec. 31, 2019
Restricted Investments Note [Abstract]
Restricted Equity Securities	Restricted Equity Securities Investments in the restricted equity securities of various entities are as follows: At December 31, 2019 2018 (In Thousands) FHLBB stock $ 35,482 $ 43,655 FRB stock 18,084 17,995 Other restricted equity securities 252 101 $ 53,818 $ 61,751 The Company invests in the stock of FHLBB as one of the requirements to borrow. As of December 31, 2019 and 2018 , FHLBB stock is recorded at its carrying value, which is equal to cost and which management believes approximates its fair value. The FHLBB stated that it remained in compliance with all regulatory capital ratios as of December 31, 2019 and was classified as "adequately capitalized" by its regulator, based on the FHLBB's financial information as of September 30, 2019. The FHLBB paid a dividend to member banks at an annualized rate of 556 basis points in 2019. The FHLBB increased its dividend from 617 basis points in the first quarter of 2019 to 587 basis points in the fourth quarter of 2019 . As of December 31, 2019 , the Company's investment in FHLBB stock exceeded its required investment which provides for additional borrowing capacity. The Company invests in the stock of the Federal Reserve Bank of Boston as required by its the Banks' membership in the Federal Reserve system. As of December 31, 2019 and 2018 , Federal Reserve Bank of Boston stock is recorded at its carrying value, which is equal to cost and which management believes approximates its fair value.

Loans and Leases

Loans and Leases	12 Months Ended
	Dec. 31, 2019
Receivables [Abstract]
Loans and Leases	Loans and Leases The following tables present loan and lease balances and weighted average coupon rates for the originated and acquired loan and lease portfolios at the dates indicated: At December 31, 2019 Originated Acquired Total Balance Weighted Average Coupon Balance Weighted Average Coupon Balance Weighted Average Coupon (Dollars In Thousands) Commercial real estate loans: Commercial real estate $ 2,400,037 4.32 % $ 90,974 4.63 % $ 2,491,011 4.33 % Multi-family mortgage 896,482 4.18 % 35,681 4.59 % 932,163 4.20 % Construction 239,015 5.04 % 7,033 6.73 % 246,048 5.09 % Total commercial real estate loans 3,535,534 4.33 % 133,688 4.73 % 3,669,222 4.34 % Commercial loans and leases: Commercial 713,875 4.65 % 15,627 5.14 % 729,502 4.66 % Equipment financing 1,049,997 7.71 % 2,411 5.98 % 1,052,408 7.71 % Condominium association 56,838 4.84 % — — % 56,838 4.84 % Total commercial loans and leases 1,820,710 6.42 % 18,038 5.25 % 1,838,748 6.41 % Consumer loans: Residential mortgage 711,522 4.06 % 102,723 4.40 % 814,245 4.10 % Home equity 343,247 4.41 % 33,572 4.93 % 376,819 4.46 % Other consumer 38,674 4.44 % 108 17.91 % 38,782 4.48 % Total consumer loans 1,093,443 4.18 % 136,403 4.54 % 1,229,846 4.22 % Total loans and leases $ 6,449,687 4.89 % $ 288,129 4.67 % $ 6,737,816 4.88 % At December 31, 2018 Originated Acquired Total Balance Weighted Average Coupon Balance Weighted Average Coupon Balance Weighted Average Coupon (Dollars In Thousands) Commercial real estate loans: Commercial real estate $ 2,208,904 4.61 % $ 121,821 4.62 % $ 2,330,725 4.61 % Multi-family mortgage 799,813 4.51 % 47,898 4.58 % 847,711 4.51 % Construction 151,138 5.62 % 22,162 6.74 % 173,300 5.76 % Total commercial real estate loans 3,159,855 4.63 % 191,881 4.85 % 3,351,736 4.64 % Commercial loans and leases: Commercial 712,630 4.96 % 23,788 5.39 % 736,418 4.97 % Equipment financing 978,840 7.61 % 3,249 5.97 % 982,089 7.60 % Condominium association 50,451 4.70 % — — % 50,451 4.70 % Total commercial loans and leases 1,741,921 6.44 % 27,037 5.46 % 1,768,958 6.43 % Consumer loans: Residential mortgage 653,059 4.09 % 129,909 4.45 % 782,968 4.15 % Home equity 331,014 5.05 % 45,470 5.39 % 376,484 5.09 % Other consumer 23,260 5.55 % 110 17.81 % 23,370 5.61 % Total consumer loans 1,007,333 4.44 % 175,489 4.70 % 1,182,822 4.48 % Total loans and leases $ 5,909,109 5.13 % $ 394,407 4.83 % $ 6,303,516 5.11 % The net unamortized deferred loan origination fees and costs included in total loans and leases were $15.7 million and $15.6 million as of December 31, 2019 and 2018 , respectively. The Company's Banks and subsidiaries lend primarily in eastern Massachusetts, southern New Hampshire and Rhode Island, with the exception of equipment financing, 28.1% of which is in the greater New York and New Jersey metropolitan area and 71.9% of which is in other areas in the United States of America as of December 31, 2019 , as compared to 26.8% of which is in the greater New York and New Jersey metropolitan area and 73.2% of which is in other areas in the United States of America as of December 31, 2018 . Accretable Yield for the Acquired Loan Portfolio The following table summarizes activity in the accretable yield for the acquired loan portfolio for the periods indicated: Year Ended December 31, 2019 2018 2017 (In Thousands) Balance at beginning of year $ 7,905 $ 10,522 $ 14,353 Accretion (3,769 ) (4,117 ) (7,801 ) Reclassification from nonaccretable difference as a result from changes in expected cash flows 1,086 1,500 3,970 Balance at end of year $ 5,222 $ 7,905 $ 10,522 On a quarterly basis, subsequent to acquisition, management reforecasts the expected cash flows for acquired ASC 310-30 loans, taking into account prepayment speeds, probability of default and loss given defaults. Management compares cash flow projections per the reforecast to the original cash flow projections and determines whether any reduction in cash flow expectations are due to deterioration, or if the change in cash flow expectation is related to noncredit events. This cash flow analysis is used to evaluate the need for a provision for loan and lease losses and/or prospective yield adjustments. These accretable yield adjustments, which are subject to continued re-assessment, will be recognized over the remaining lives of those pools. Related Party Loans The Banks' authority to extend credit to their respective directors and executive officers, as well as to entities controlled by such persons, is currently governed by the requirements of the Sarbanes-Oxley Act and Regulation O of the FRB. Among other things, these provisions require that extensions of credit to insiders (1) be made on terms that are substantially the same as, and follow credit underwriting procedures that are not less stringent than, those prevailing for comparable transactions with unaffiliated persons and that do not involve more than the normal risk of repayment or present other unfavorable features; and (2) not exceed certain limitations on the amount of credit extended to such persons, individually and in the aggregate, which limits are based, in part, on the amount of the Banks' capital. In addition, the extensions of credit to insiders must be approved by the applicable Bank's Board of Directors. The following table summarizes the change in the total amounts of loans and advances, to directors, executive officers and their affiliates for the periods indicated. All loans were performing as of December 31, 2019 . Year Ended December 31, 2019 2018 (In Thousands) Balance at beginning of year $ 46,771 $ 47,941 New loans granted during the year 34 2,842 Loans reclassified as insider loans 16,800 — Advances on lines of credit 8,652 193 Repayments (1,857 ) (4,205 ) Balance at end of year $ 70,400 $ 46,771 Unfunded commitments on extensions of credit to related parties totaled $12.8 million and $5.9 million as of December 31, 2019 and 2018 , respectively. Loans and Leases Pledged as Collateral As of December 31, 2019 and 2018 , there were $3.0 billion and $3.0 billion , respectively, of loans and leases pledged as collateral for repurchase agreements; municipal deposits; treasury, tax and loan deposits; swap agreements; and FHLBB borrowings. The Banks did not have any outstanding FRB borrowings as of December 31, 2019 and 2018 .

Allowance for Loan and Lease Lo

Allowance for Loan and Lease Losses	12 Months Ended
	Dec. 31, 2019
Receivables [Abstract]
Allowance for Loan and Lease Losses	Allowance for Loan and Lease Losses The following tables present the changes in the allowance for loan and lease losses and the recorded investment in loans and leases by portfolio segment for the periods indicated: Year Ended December 31, 2019 Commercial Real Estate Commercial Consumer Total (In Thousands) Balance at December 31, 2018 $ 28,187 $ 25,283 $ 5,222 $ 58,692 Charge-offs — (8,911 ) (127 ) (9,038 ) Recoveries — 1,688 179 1,867 Provision for loan and lease losses 2,098 6,766 697 9,561 Balance at December 31, 2019 $ 30,285 $ 24,826 $ 5,971 $ 61,082 Year Ended December 31, 2018 Commercial Real Estate Commercial Consumer Total (In Thousands) Balance at December 31, 2017 $ 27,112 $ 26,333 $ 5,147 $ 58,592 Charge-offs (103 ) (6,585 ) (540 ) (7,228 ) Recoveries — 2,287 290 2,577 Provision for loan and lease losses 1,178 3,248 325 4,751 Balance at December 31, 2018 $ 28,187 $ 25,283 $ 5,222 $ 58,692 Year Ended December 31, 2017 Commercial Real Estate Commercial Consumer Total (In Thousands) Balance at December 31, 2016 $ 27,645 $ 20,906 $ 5,115 $ 53,666 Charge-offs (494 ) (14,914 ) (403 ) (15,811 ) Recoveries 476 1,158 319 1,953 (Credit) provision for loan and lease losses (515 ) 19,183 116 18,784 Balance at December 31, 2017 $ 27,112 $ 26,333 $ 5,147 $ 58,592 The liability for unfunded credit commitments, which is included in other liabilities, remained $1.9 million , at December 31, 2019 , and 2018 , respectively. The changes in the liability for unfunded credit commitments reflect changes in the estimate of loss exposure associated with certain unfunded credit commitments. No credit commitments were charged off against the liability account in the years ended December 31, 2019 , and 2018 . Provision for Credit Losses The provisions for credit losses are set forth below for the periods indicated: Originated Acquired Total Year Ended December 31, Year Ended December 31, Year Ended December 31, 2019 2018 2017 2019 2018 2017 2019 2018 2017 (In Thousands) Provision (credit) for loan and lease losses: Commercial real estate $ 1,798 $ 254 $ (343 ) $ 300 $ 924 $ (172 ) $ 2,098 $ 1,178 $ (515 ) Commercial 6,539 3,699 18,899 227 (451 ) 284 6,766 3,248 19,183 Consumer 713 556 273 (16 ) (231 ) (157 ) 697 325 116 Total provision (credit) for loan and lease losses 9,050 4,509 18,829 511 242 (45 ) 9,561 4,751 18,784 Unfunded credit commitments 22 200 204 — — — 22 200 204 Total provision (credit) for credit losses $ 9,072 $ 4,709 $ 19,033 $ 511 $ 242 $ (45 ) $ 9,583 $ 4,951 $ 18,988 Allowance for Loan and Lease Losses Methodology Management has established a methodology to determine the adequacy of the allowance for loan and lease losses that assesses the risks and losses inherent in the loan and lease portfolio. Additions to the allowance for loan and lease losses are made by charges to the provision for credit losses. Losses on loans and leases are charged off against the allowance when all or a portion of a loan or lease is considered uncollectible. Subsequent recoveries on loans previously charged off, if any, are credited to the allowance when realized. For each class of loan, management makes significant judgments in selecting the estimation method that fits the credit characteristics of its class and portfolio segment as set forth below. Also refer to Note 1, "Basis of Presentation," in the consolidated financial statements for more information on the Company's allowance of loan and lease losses methodology. As of December 31, 2019 , management believes that the methodology for calculating the allowance provides a reasonable basis for determining and reporting on probable losses in the Company’s loan portfolios. As of December 31, 2019 , the Company had a portfolio of approximately $10.3 million in loans secured by taxi medallions issued by the cities of Boston and Cambridge. As of December 31, 2018 , this portfolio was approximately $13.7 million . Application-based mobile ride services, such as Uber and Lyft, have generated increased competition in the transportation sector, resulting in a reduction in taxi utilization and, as a result, a reduction in the collateral value and credit quality of taxi medallion loans. This has increased the likelihood that loans secured by taxi medallions may default, or that the borrowers may be unable to repay these loans at maturity, resulting in an increase in past due loans, troubled debt restructurings, and charge-offs. Therefore, beginning with the three months ended September 30, 2015, the Company’s allowance calculation included an enhanced segmentation of the commercial loans and leases to reflect the increased risk in the Company’s taxi medallion portfolio. This allowance calculation segmentation represents management’s estimations of the special risks associated with the taxi portfolio. As of December 31, 2019 , the Company had an allowance for loan and lease losses associated with taxi medallion loans of $2.1 million of which $0.6 million were specific reserves and $1.5 million was a general reserve. As of December 31, 2018 , the Company had a reserve for loan and lease losses associated with taxi medallion loans of $2.5 million of which $1.9 million were specific reserves and $0.6 million was a general reserve. The decrease in the allowance for loans associated with taxi medallion loans was primarily driven by the decrease in specific reserves due to charge-offs, partially offset by the increase in the general reserve due to the downgrade of a taxi relationship. The total troubled debt restructured loans secured by taxi medallions decreased from $3.7 million at December 31, 2018 to $1.0 million at December 31, 2019 . The total loans secured by taxi medallions that were placed on nonaccrual decreased to $1.3 million at December 31, 2019 from $3.7 million at December 31, 2018 . The decrease in total loans secured by taxi medallions was primarily driven by the net charge-offs of $1.7 million and the pay down in taxi medallion loans. Further declines in demand for taxi services or further deterioration in the value of taxi medallions may result in higher delinquencies and losses beyond that provided for in the allowance for loan and lease losses. The general allowance for loan and lease losses was $59.3 million as of December 31, 2019 , compared to $55.6 million as of December 31, 2018 . The general portion of the allowance for loan and lease losses increased by $3.7 million during the year ended December 31, 2019 , as a result of the continued growth in the Company's loan portfolios, partly offset by decreases in historical loss factors applied to the commercial real estate and commercial loan portfolios. The specific allowance for loan and lease losses was $1.8 million as of December 31, 2019 , compared to $3.1 million as of December 31, 2018 . The specific allowance for loan and lease losses decreased by $1.3 million during the year ended December 31, 2019 , which was primarily driven by the charge-offs on the specific reserves for taxi medallion loans during the year. Credit Quality Assessment At the time of loan origination, a rating is assigned based on the capacity to pay and general financial strength of the borrower, the value of assets pledged as collateral, and the evaluation of third party support such as a guarantor. The Company periodically monitors the quality of the loan portfolio using all available information. The officer responsible for handling each loan is required to initiate changes to risk ratings when changes in facts and circumstances occur that warrant an upgrade or downgrade in a loan rating. Based on this information, loans demonstrating certain payment issues or other weaknesses may be categorized as delinquent, impaired, nonperforming and/or put on nonaccrual status. Additionally, in the course of resolving such loans, the Company may choose to restructure the contractual terms of certain loans to match the borrower's ability to repay the loan based on their current financial condition. If a restructured loan meets certain criteria, it may be categorized as a troubled debt restructuring. The Company reviews numerous credit quality indicators when assessing the risk in its loan portfolio. For all loans, the Company utilizes an eight-grade loan rating system, which assigns a risk rating to each borrower based on a number of quantitative and qualitative factors associated with a loan transaction. Factors considered include industry and market conditions; position within the industry; earnings trends; operating cash flow; asset/liability values; debt capacity; guarantor strength; management and controls; financial reporting; collateral; and other considerations. In addition, the Company's independent loan review group evaluates the credit quality and related risk ratings in all loan portfolios. The results of these reviews are reported to the Risk Committee of the Board of Directors on a periodic basis and annually to the Board of Directors. For the consumer loans, the Company heavily relies on payment status for calibrating credit risk. The ratings categories used for assessing credit risk in the commercial real estate, multi-family mortgage, construction, commercial, equipment financing, condominium association and other consumer loan and lease classes are defined as follows: 1 -4 Rating—Pass Loan rating grades "1" through "4" are classified as "Pass," which indicates borrowers are performing in accordance with the terms of the loan and are less likely to result in loss due to the capacity of the borrower to pay and the adequacy of the value of assets pledged as collateral. 5 Rating—Other Assets Especially Mentioned ("OAEM") Borrowers exhibit potential credit weaknesses or downward trends deserving management's attention. If not checked or corrected, these trends will weaken the Company's asset and position. While potentially weak, currently these borrowers are marginally acceptable; no loss of principal or interest is envisioned. 6 Rating—Substandard Borrowers exhibit well defined weaknesses that jeopardize the orderly liquidation of debt. Substandard loans may be inadequately protected by the current net worth and paying capacity of the obligors or by the collateral pledged, if any. Normal repayment from the borrower is in jeopardy. Although no loss of principal is envisioned, there is a distinct possibility that a partial loss of interest and/or principal will occur if the deficiencies are not corrected. Collateral coverage may be inadequate to cover the principal obligation. 7 Rating—Doubtful Borrowers exhibit well-defined weaknesses that jeopardize the orderly liquidation of debt with the added provision that the weaknesses make collection of the debt in full, on the basis of currently existing facts, conditions, and values, highly questionable and improbable. Serious problems exist to the point where partial loss of principal is likely. 8 Rating—Definite Loss Borrowers deemed incapable of repayment. Loans to such borrowers are considered uncollectible and of such little value that continuation as active assets of the Company is not warranted. Assets rated as "OAEM," "substandard" or "doubtful" based on criteria established under banking regulations are collectively referred to as "criticized" assets. Credit Quality Information The following tables present the recorded investment in loans in each class as of December 31, 2019 by credit quality indicator. At December 31, 2019 Commercial Real Estate Multi- Family Mortgage Construction Commercial Equipment Financing Condominium Association Other Consumer Total (In Thousands) Originated: Loan rating: Pass $ 2,379,925 $ 896,398 $ 239,015 $ 688,268 $ 1,038,793 $ 56,687 $ 38,673 $ 5,337,759 OAEM 17,006 — — 10,803 1,389 — — 29,198 Substandard 3,106 84 — 14,801 7,995 151 1 26,138 Doubtful — — — 3 1,820 — — 1,823 Total originated 2,400,037 896,482 239,015 713,875 1,049,997 56,838 38,674 5,394,918 Acquired: Loan rating: Pass 81,360 35,681 7,033 15,215 2,404 — 108 141,801 OAEM 597 — — 210 — — — 807 Substandard 9,017 — — 202 7 — — 9,226 Total acquired 90,974 35,681 7,033 15,627 2,411 — 108 151,834 Total loans $ 2,491,011 $ 932,163 $ 246,048 $ 729,502 $ 1,052,408 $ 56,838 $ 38,782 $ 5,546,752 As of December 31, 2019 , there were no loans categorized as definite loss. At December 31, 2019 Residential Mortgage Home Equity ($ In Thousands) Originated: Loan-to-value ratio: Less than 50% $ 184,628 22.7 % $ 132,736 35.2 % 50% - 69% 293,976 36.1 % 91,681 24.3 % 70% - 79% 204,600 25.1 % 81,459 21.6 % 80% and over 25,664 3.2 % 37,371 9.9 % Data not available* 2,654 0.3 % — — % Total originated 711,522 87.4 % 343,247 91.0 % Acquired: Loan-to-value ratio: Less than 50% 32,838 4.0 % 16,882 4.5 % 50%—69% 44,754 5.4 % 7,958 2.1 % 70%—79% 14,305 1.8 % 705 0.2 % 80% and over 4,608 0.6 % 4,726 1.3 % Data not available* 6,218 0.8 % 3,301 0.9 % Total acquired 102,723 12.6 % 33,572 9.0 % Total loans $ 814,245 100.0 % $ 376,819 100.0 % _______________________________________________________________________________ * Represents accounts for which data are not available. The following tables present the recorded investment in loans in each class as of December 31, 2018 by credit quality indicator. At December 31, 2018 Commercial Real Estate Multi- Family Mortgage Construction Commercial Equipment Financing Condominium Association Other Consumer Total (In Thousands) Originated: Loan rating: Pass $ 2,198,377 $ 799,483 $ 150,742 $ 685,773 $ 969,275 $ 50,186 $ 23,249 $ 4,877,085 OAEM 6,096 — — 3,726 52 — — 9,874 Substandard 4,431 330 396 22,870 6,895 265 11 35,198 Doubtful — — — 261 2,618 — — 2,879 Total originated 2,208,904 799,813 151,138 712,630 978,840 50,451 23,260 4,925,036 Acquired: Loan rating: Pass 111,919 47,715 22,162 23,250 3,240 — 110 208,396 OAEM 626 — — 236 — — — 862 Substandard 9,276 183 — 302 9 — — 9,770 Total acquired 121,821 47,898 22,162 23,788 3,249 — 110 219,028 Total loans $ 2,330,725 $ 847,711 $ 173,300 $ 736,418 $ 982,089 $ 50,451 $ 23,370 $ 5,144,064 As of December 31, 2018 , there were no loans categorized as definite loss. At December 31, 2018 Residential Mortgage Home Equity ($ In Thousands) Originated: Loan-to-value ratio: Less than 50% $ 171,523 21.9 % $ 142,534 37.9 % 50%—69% 287,337 36.7 % 84,423 22.4 % 70%—79% 173,870 22.2 % 73,898 19.6 % 80% and over 19,030 2.4 % 30,129 8.0 % Data not available* 1,299 0.2 % 30 — % Total originated 653,059 83.4 % 331,014 87.9 % Acquired: Loan-to-value ratio: Less than 50% 36,752 4.6 % 24,705 6.6 % 50%—69% 53,788 6.9 % 10,353 2.7 % 70%—79% 26,510 3.4 % 1,000 0.3 % 80% and over 6,701 0.9 % 4,348 1.2 % Data not available* 6,158 0.8 % 5,064 1.3 % Total acquired 129,909 16.6 % 45,470 12.1 % Total loans $ 782,968 100.0 % $ 376,484 100.0 % _______________________________________________________________________________ * Represents accounts for which data are not available. The following table presents information regarding foreclosed residential real estate property for the periods indicated: At December 31, 2019 At December 31, 2018 (In Thousands) Recorded investment in mortgage loans collateralized by residential real estate property that are in the process of foreclosure $ 110 $ 121 Age Analysis of Past Due Loans and Leases The following tables present an age analysis of the recorded investment in total loans and leases as of December 31, 2019 and 2018 . At December 31, 2019 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (In Thousands) Originated: Commercial real estate loans: Commercial real estate $ 3,330 $ 2,032 $ 1,606 $ 6,968 $ 2,393,069 $ 2,400,037 $ 51 $ 2,751 Multi-family mortgage 3,559 553 — 4,112 892,370 896,482 — 84 Construction — — — — 239,015 239,015 — — Total commercial real estate loans 6,889 2,585 1,606 11,080 3,524,454 3,535,534 51 2,835 Commercial loans and leases: Commercial 5,010 199 3,875 9,084 704,791 713,875 — 4,707 Equipment financing 3,098 1,558 7,246 11,902 1,038,095 1,049,997 — 9,822 Condominium association 458 — — 458 56,380 56,838 — 151 Total commercial loans and leases 8,566 1,757 11,121 21,444 1,799,266 1,820,710 — 14,680 Consumer loans: Residential mortgage 1,014 — 3 1,017 710,505 711,522 — 753 Home equity 794 501 139 1,434 341,813 343,247 2 276 Other consumer 46 1 1 48 38,626 38,674 — 1 Total consumer loans 1,854 502 143 2,499 1,090,944 1,093,443 2 1,030 Total originated loans and leases $ 17,309 $ 4,844 $ 12,870 $ 35,023 $ 6,414,664 $ 6,449,687 $ 53 $ 18,545 (Continued) At December 31, 2019 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (1) (In Thousands) Acquired: Commercial real estate loans: Commercial real estate $ 539 $ 59 $ 8,989 $ 9,587 $ 81,387 $ 90,974 $ 8,919 $ 94 Multi-family mortgage — — — — 35,681 35,681 — — Construction — — — — 7,033 7,033 — — Total commercial real estate loans 539 59 8,989 9,587 124,101 133,688 8,919 94 Commercial loans and leases: Commercial — — — — 15,627 15,627 — 202 Equipment financing — — 7 7 2,404 2,411 7 — Total commercial loans and leases — — 7 7 18,031 18,038 7 202 Consumer loans: Residential mortgage 35 75 1,090 1,200 101,523 102,723 1,090 — Home equity 430 — 42 472 33,100 33,572 40 620 Other consumer — — — — 108 108 — — Total consumer loans 465 75 1,132 1,672 134,731 136,403 1,130 620 Total acquired loans and leases 1,004 134 10,128 11,266 276,863 288,129 10,056 916 Total loans and leases $ 18,313 $ 4,978 $ 22,998 $ 46,289 $ 6,691,527 $ 6,737,816 $ 10,109 $ 19,461 (1) Loans and leases acquired with deteriorated credit quality are always accruing. At December 31, 2018 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (In Thousands) Originated: Commercial real estate loans: Commercial real estate $ 5,139 $ 896 $ 2,962 $ 8,997 $ 2,199,907 $ 2,208,904 $ 277 $ 3,806 Multi-family mortgage 893 — 145 1,038 798,775 799,813 — 330 Construction 297 — 396 693 150,445 151,138 — 396 Total commercial real estate loans 6,329 896 3,503 10,728 3,149,127 3,159,855 277 4,532 Commercial loans and leases: Commercial 2,021 582 6,244 8,847 703,783 712,630 1,962 6,421 Equipment financing 2,509 650 5,685 8,844 969,996 978,840 12 9,500 Condominium association 320 — — 320 50,131 50,451 — 265 Total commercial loans and leases 4,850 1,232 11,929 18,011 1,723,910 1,741,921 1,974 16,186 Consumer loans: Residential mortgage 400 — 1,597 1,997 651,062 653,059 — 1,842 Home equity 761 25 183 969 330,045 331,014 1 191 Other consumer 51 18 15 84 23,176 23,260 — 17 Total consumer loans 1,212 43 1,795 3,050 1,004,283 1,007,333 1 2,050 Total originated loans and leases $ 12,391 $ 2,171 $ 17,227 $ 31,789 $ 5,877,320 $ 5,909,109 $ 2,252 $ 22,768 (Continued) At December 31, 2018 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (In Thousands) Acquired: Commercial real estate loans: Commercial real estate $ — $ 215 $ 9,087 $ 9,302 $ 112,519 $ 121,821 $ 9,018 $ 122 Multi-family mortgage 348 — — 348 47,550 47,898 — — Construction 360 242 — 602 21,560 22,162 — — Total commercial real estate loans 708 457 9,087 10,252 181,629 191,881 9,018 122 Commercial loans and leases: Commercial 124 44 290 458 23,330 23,788 90 200 Equipment financing — — 9 9 3,240 3,249 9 — Total commercial loans and leases 124 44 299 467 26,570 27,037 99 200 Consumer loans: Residential mortgage — 371 2,113 2,484 127,425 129,909 2,113 290 Home equity 191 265 2 458 45,012 45,470 — 717 Other consumer — — — — 110 110 — — Total consumer loans 191 636 2,115 2,942 172,547 175,489 2,113 1,007 Total acquired loans and leases 1,023 1,137 11,501 13,661 380,746 394,407 11,230 1,329 Total loans and leases $ 13,414 $ 3,308 $ 28,728 $ 45,450 $ 6,258,066 $ 6,303,516 $ 13,482 $ 24,097 Impaired Loans and Leases Refer to Note 1, "Basis of Presentation", in the consolidated financial statements for more information on the Company's methodology over impaired loans and leases. The following tables include the recorded investment and unpaid principal balances of impaired loans and leases with the related allowance amount, if applicable, for the originated and acquired loan and lease portfolios at the dates indicated. Also presented are the average recorded investments in the impaired loans and leases and the related amount of interest recognized during the period that the impaired loans were impaired. At December 31, 2019 At December 31, 2018 Recorded (1) Unpaid Related Recorded Investment (2) Unpaid Related (In Thousands) Originated: With no related allowance recorded: Commercial real estate $ 3,899 $ 3,892 $ — $ 5,569 $ 5,545 $ — Commercial 28,539 28,533 — 30,927 31,053 — Consumer 2,237 2,223 — 2,989 2,978 — Total originated with no related allowance recorded 34,675 34,648 — 39,485 39,576 — With an allowance recorded: Commercial real estate 68 68 7 396 396 5 Commercial 5,980 6,055 1,672 8,224 8,208 2,961 Consumer 1,224 1,220 70 665 664 89 Total originated with an allowance recorded 7,272 7,343 1,749 9,285 9,268 3,055 Total originated impaired loans and leases 41,947 41,991 1,749 48,770 48,844 3,055 Acquired: With no related allowance recorded: Commercial real estate 12,365 12,366 — 9,538 9,538 — Commercial 437 437 — 531 531 — Consumer 3,516 3,516 — 4,772 4,772 — Total acquired with no related allowance recorded 16,318 16,319 — 14,841 14,841 — With an allowance recorded: Consumer 447 447 40 154 154 26 Total acquired with an allowance recorded 447 447 40 154 154 26 Total acquired impaired loans and leases 16,765 16,766 40 14,995 14,995 26 Total impaired loans and leases $ 58,712 $ 58,757 $ 1,789 $ 63,765 $ 63,839 $ 3,081 __________________________________________________________________________ (1) Includes originated and acquired nonaccrual loans of $18.5 million and $0.9 million , respectively as of December 31, 2019 . Includes originated loans individually and collectively evaluated for impairment of $27.3 million and $14.6 million , respectively as of December 31, 2019 . Includes acquired loans individually and collectively evaluated for impairment of $5.2 million and $11.6 million , respectively as of December 31, 2019 . (2) Includes originated and acquired nonaccrual loans of $22.7 million and $1.3 million , respectively as of December 31, 2018 . Includes originated loans individually and collectively evaluated for impairment of $41.2 million and $7.6 million , respectively as of December 31, 2018 . Includes acquired loans individually and collectively evaluated for impairment of $2.5 million and $12.5 million , respectively as of December 31, 2018 . Year Ended December 31, 2019 December 31, 2018 December 31, 2017 Average Interest Average Interest Average Interest (In Thousands) Originated: With no related allowance recorded: Commercial real estate $ 5,148 $ 110 $ 6,484 $ 87 $ 10,181 $ 277 Commercial 29,759 1,009 26,514 993 24,950 747 Consumer 2,662 42 2,801 54 4,330 58 Total originated with no related allowance recorded 37,569 1,161 35,799 1,134 39,461 1,082 With an allowance recorded: Commercial real estate 269 3 99 — 3,271 162 Commercial 7,125 76 9,026 96 18,382 1 Consumer 946 32 835 11 — — Total originated with an allowance recorded 8,340 111 9,960 107 21,653 163 Total originated impaired loans and leases 45,909 1,272 45,759 1,241 61,114 1,245 Acquired: With no related allowance recorded: Commercial real estate 11,409 163 9,868 7 4,005 55 Commercial 511 11 1,212 16 2,280 31 Consumer 4,298 39 5,061 61 5,295 69 Total acquired with no related allowance recorded 16,218 213 16,141 84 11,580 155 With an allowance recorded: Consumer 302 11 135 4 151 4 Total acquired with an allowance recorded 302 11 135 4 151 4 Total acquired impaired loans and leases 16,520 224 16,276 88 11,731 159 Total impaired loans and leases $ 62,429 $ 1,496 $ 62,035 $ 1,329 $ 72,845 $ 1,404 The following tables present information regarding impaired and non-impaired loans and leases at the dates indicated: At December 31, 2019 Commercial Real Estate Commercial Consumer Total (In Thousands) Allowance for Loan and Lease Losses: Originated: Individually evaluated for impairment $ 7 $ 1,672 $ 70 $ 1,749 Collectively evaluated for impairment 28,415 22,853 5,850 57,118 Total originated loans and leases 28,422 24,525 5,920 58,867 Acquired: Individually evaluated for impairment — — 40 40 Collectively evaluated for impairment 65 197 11 273 Acquired with deteriorated credit quality 1,798 104 — 1,902 Total acquired loans and leases 1,863 301 51 2,215 Total allowance for loan and lease losses $ 30,285 $ 24,826 $ 5,971 $ 61,082 Loans and Leases: Originated: Individually evaluated for impairment $ 3,956 $ 20,019 $ 3,326 $ 27,301 Collectively evaluated for impairment 3,531,578 1,800,691 1,090,117 6,422,386 Total originated loans and leases 3,535,534 1,820,710 1,093,443 6,449,687 Acquired: Individually evaluated for impairment 2,942 397 1,841 5,180 Collectively evaluated for impairment 79,465 15,465 110,758 205,688 Acquired with deteriorated credit quality 51,281 2,176 23,804 77,261 Total acquired loans and leases 133,688 18,038 136,403 288,129 Total loans and leases $ 3,669,222 $ 1,838,748 $ 1,229,846 $ 6,737,816 At December 31, 2018 Commercial Real Estate Commercial Consumer Total (In Thousands) Allowance for Loan and Lease Losses: Originated: Individually evaluated for impairment $ 5 $ 2,961 $ 89 $ 3,055 Collectively evaluated for impairment 26,617 22,131 5,075 53,823 Total originated loans and leases 26,622 25,092 5,164 56,878 Acquired: Individually evaluated for impairment — — 26 26 Collectively evaluated for impairment 32 83 20 135 Acquired with deteriorated credit quality 1,533 108 12 1,653 Total acquired loans and leases 1,565 191 58 1,814 Total allowance for loan and lease losses $ 28,187 $ 25,283 $ 5,222 $ 58,692 Loans and Leases: Originated: Individually evaluated for impairment $ 5,610 $ 32,127 $ 3,502 $ 41,239 Collectively evaluated for impairment 3,154,245 1,709,794 1,003,831 5,867,870 Total originated loans and leases 3,159,855 1,741,921 1,007,333 5,909,109 Acquired: Individually evaluated for impairment — 404 2,072 2,476 Collectively evaluated for impairment 121,119 24,094 142,194 287,407 Acquired with deteriorated credit quality 70,762 2,539 31,223 104,524 Total acquired loans and leases 191,881 27,037 175,489 394,407 Total loans and leases $ 3,351,736 $ 1,768,958 $ 1,182,822 $ 6,303,516 Troubled Debt Restructured Loans and Leases A specific valuation allowance for losses on troubled debt restructured loans is initially determined by comparing the net carrying amount of the troubled debt restructured loan with the restructured loan's cash flows discounted at the original effective rate. The following table sets forth information regarding troubled debt restructured loans and leases at the dates indicated: At December 31, 2019 At December 31, 2018 (In Thousands) Troubled debt restructurings: On accrual $ 17,076 $ 12,257 On nonaccrual 6,104 8,684 Total troubled debt restructurings $ 23,180 $ 20,941 Total troubled debt restructuring loans and leases increased by $2.3 million to $23.2 million at December 31, 2019 from $20.9 million at December 31, 2018 , primarily driven by one construction loan of $2.9 million which became a TDR during the year, partially offset by the payoff and pay down of current troubled debt restructuring loans during the year. The recorded investment in troubled debt restructurings and the associated specific allowances for loan and lease losses, in the originated and acquired loan and lease portfolios, that were modified during the periods indicated, are as follows. At and for the Year Ended December 31, 2019 Recorded Investment Specific Allowance for Loan and Lease Losses Defaulted (1) Number of Loans/ Leases At Modification At End of Period Nonaccrual Loans and Leases Number of Loans/ Leases Recorded Investment (Dollars in Thousands) Originated: Commercial real estate 2 $ 295 $ 290 $ — $ 221 — $ — Commercial 3 6,794 5,457 2,455 1,912 1 1,912 Equipment financing 7 2,774 2,266 — 392 2 365 Residential mortgage 3 868 866 — 96 — — Home equity 3 453 453 — — — — Total originated 18 11,184 9,332 2,455 2,621 3 2,277 Acquired: Construction 1 4,869 2,942 — — — — Residential mortgage 1 297 295 — — — — Home equity 1 134 133 — 133 — — Total acquired 3 5,300 3,370 — 133 — — Total loans and leases 21 $ 16,484 $ 12,702 $ 2,455 $ 2,754 3 $ 2,277 ______________________________________________________________________ (1) Includes loans and leases that have been modified within the past twelve months and subsequently had payment defaults during the period indicated. At and for the Year Ended December 31, 2018 Recorded Investment Specific Allowance for Loan and Lease Losses Defaulted (1) Number of Loans/ Leases At Modification At End of Period Nonaccrual Loans and Leases Number of Loans/ Leases Recorded Investment (Dollars in Thousands) Originated: Commercial real estate 1 $ 673 $ 652 $ — $ 653 — $ — Commercial 10 1,775 1,706 733 1,706 2 1,075 Equipment financing 14 2,510 2,556 37 1,351 — — Residential mortgage 2 550 550 12 341 1 341 Home equity 1 86 83 — — — — Total originated 28 $ 5,594 $ 5,547 $ 782 $ 4,051 3 $ 1,416 Acquired: Home equity 2 249 245 — 245 — — Total acquired 2 249 245 — 245 — — Total loans and leases 30 $ 5,843 $ 5,792 $ 782 $ 4,296 3 $ 1,416 ______________________________________________________________________ (1) Includes loans and leases that have been modified within the past twelve months and subsequently had payment defaults during the period indicated. At and for the Year Ended December 31, 2017 Recorded Investment Specific Allowance for Loan and Lease Losses Defaulted (1) Number of Loans/ Leases At Modification At End of Period Nonaccrual Loans and Leases Number of Loans/ Leases Recorded Investment (Dollars in Thousands) Originated: Commercial real estate 1 $ 189 $ 189 $ — $ — — $ — Commercial 10 7,861 3,911 191 2,189 2 1,361 Equipment financing 16 2,687 2,901 137 1,440 1 188 Total originated 27 10,737 7,001 328 3,629 3 1,549 ______________________________________________________________________ (1) Includes loans and leases that have been modified within the past twelve months and subsequently had payment defaults during the period indicated. There were no acquired loans and leases that met the definition of a troubled debt restructured during the twelve months ended December 31, 2017 . The following table sets forth the Company's end-of-period balances for troubled debt restructurings that were modified during the periods indicated, by type of modification. Year Ended December 31, 2019 2018 2017 (In Thousands) Loans with one modification: Extended maturity $ 5,811 $ 1,717 $ 2,810 Adjusted principal — — 19 Adjusted interest rate 252 — — Interest only — — 174 Combination maturity, principal, interest rate 3,624 3,651 1,914 Total loans modified once $ 9,687 $ 5,368 $ 4,917 Loans with more than one modification: Extended maturity $ 3,015 $ — $ 1,910 Combination maturity, principal, interest rate — 424 174 Total loans modified more than once $ 3,015 $ 424 $ 2,084 Total loans modified $ 12,702 $ 5,792 $ 7,001 The increase in troubled debt restructuring loans and leases that were modified for the year ending December 31, 2019 was primarily due to the increases in modifications on the commercial loans by $3.6 million and construction loans by $2.9 million during the year. The net charge-offs of the performing and nonperforming troubled debt restructuring loans and leases for the years ending December 31, 2019 , 2018 , and 2017 were $2.0 million , $1.2 million , and $4.8 million , respectively. The increase in net charge-offs of the performing and nonperforming troubled debt restructuring loans and leases for the year ending December 31, 2019 was primarily driven by the charge-offs on various taxi medallion relationships during the year. As of December 31, 2019 , loans modified to troubled debt restructurings totaled $3.1 million . As of December 31, 2018 , and 2017 the Company did not have any loans modified to trouble debt restructurings.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment Premises and equipment consist of the following: At December 31, Estimated Useful Life 2019 2018 (In Thousands) (In Years) Land $ 12,320 $ 12,300 NA Fine art 545 533 NA Computer equipment 11,886 10,488 3 Vehicles 135 126 3 to 5 Core processing system and software 20,748 20,466 3 to 7.5 Furniture, fixtures and equipment 15,393 14,696 5 to 25 Office building and improvements 90,086 87,913 10 to 40 Total 151,113 146,522 Accumulated depreciation and amortization 76,763 70,140 Total premises and equipment $ 74,350 $ 76,382 Depreciation and amortization expense is calculated using the straight-line method and is included in occupancy and equipment and data processing expense in the Consolidated Statements of Income. For the years ended December 31, 2019 , 2018 and 2017 , depreciation and amortization expense related to premises and equipment totaled $7.0 million , $7.5 million , and $7.4 million , respectively. During the year the Company made office improvements to three locations and upgraded the computer system throughout the Company.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The changes in the carrying value of goodwill for the periods indicated were as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Balance at beginning of year $ 160,427 $ 137,890 $ 137,890 Additions — 22,537 — Balance at end of year $ 160,427 $ 160,427 $ 137,890 The following is a summary of the Company's other intangible assets: At December 31, 2019 At December 31, 2018 Gross Accumulated Carrying Gross Accumulated Carrying (In Thousands) Other intangible assets: Core deposits $ 38,294 $ 34,960 $ 3,334 $ 38,294 $ 33,297 $ 4,997 Trade name 1,600 511 1,089 1,600 511 1,089 Trust relationship 1,568 1,568 — 1,568 1,568 — Other intangible 442 442 — 442 442 — Total other intangible assets $ 41,904 $ 37,481 $ 4,423 $ 41,904 $ 35,818 $ 6,086 At December 31, 2013, the Company concluded that the BankRI name would continue to be utilized in its marketing strategies; therefore, the trade name with carrying value of $1.1 million , has an indefinite life and ceased to amortize. The weighted-average amortization period for the core deposit intangible is 7.04 years . There were no impairment losses relating to other acquisition-related intangible assets recorded during the years ended December 31, 2019 , 2018 and 2017 . The estimated aggregate future amortization expense for other intangible assets for each of the next five years and thereafter is as follows: Year ended December 31: Amount (In Thousands) 2020 $ 1,297 2021 850 2022 494 2023 263 2024 153 Thereafter 277 Total $ 3,334

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	Other Assets BOLI BOLI is recorded at the cash surrender value of the policies, less any applicable cash surrender charges, and is recorded in other assets. As of December 31, 2019 and 2018 , BankRI owned seven policies with a net cash surrender value of $41.0 million and $39.9 million , respectively. As of December 31, 2019 and 2018 , Brookline Bank, as successor-in-interest to First Ipswich owned two policies with a net cash surrender value of $0.8 million , respectively. The Company recorded a total of $1.0 million , $1.0 million , and $1.0 million of tax exempt income from these nine policies in 2019 , 2018 , and 2017 , respectively. They are included in the Company’s other non-interest income in the consolidated statements of income. Affordable Housing Investments The Company began investing in affordable housing projects that benefit low- and moderate-income individuals in 2009. As of December 31, 2019 , the Company had investments in 17 of these projects. The project sponsor or general partner controls the project's management. In each case, the Company is a limited partner with less than 50% of the outstanding equity interest in any single project. On January 1, 2015, the Company adopted ASU 2014-01, Accounting for Investments in Qualified Affordable Housing Projects , which required retrospective application and had an impact on net income for 2014 of $0.5 million and a cumulative effect on retained earnings of $1.1 million at January 1, 2015. Prior to the adoption of ASU 2014-01, the Company’s investments in qualified affordable housing projects were accounted for using the equity method. Under the equity method, operating losses or gains from these investments were included as a component of non-interest income in the Company's consolidated statements of income. ASU 2014-01 calls for the use of the proportional amortization method calculation and the operating losses or gains for these investments are included as a component of the provision for income taxes in the Company’s consolidated statements of income. Under the proportional amortization method, the initial costs of the investment in qualified affordable housing projects is amortized based on the tax credits and other benefits received. Further information regarding the Company's investments in affordable housing projects follows: At December 31, 2019 2018 (In Thousands) Investments in affordable housing projects included in other assets $ 29,939 $ 10,895 Unfunded commitments related to affordable housing projects included in other liabilities 20,286 1,115 Investment in affordable housing tax credits 2,042 1,885 Investment in affordable housing tax benefits 540 585 For the year ended December 31, 2019 2018 2017 (In Thousands) Investment amortization included in provision for income taxes $ 2,097 $ 1,916 $ 1,844 Amount recognized as income tax benefit 540 585 623

Deposits

Deposits	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Deposits	Deposits A summary of deposits follows: December 31, 2019 December 31, 2018 Amount Weighted Average Rate Amount Weighted Average Rate (Dollars in Thousands) Demand checking accounts $ 1,141,578 — % $ 1,033,551 — % NOW accounts 371,380 0.11 % 336,317 0.10 % Savings accounts 613,467 0.46 % 619,961 0.32 % Money market accounts 1,682,005 1.15 % 1,675,050 1.18 % Total core deposit accounts 3,808,430 0.59 % 3,664,879 0.60 % Certificate of deposit accounts maturing: Within six months 730,512 2.24 % 475,303 1.20 % After six months but within 1 year 650,461 2.24 % 562,018 1.40 % After 1 year but within 2 years 495,509 2.26 % 538,435 1.85 % After 2 years but within 3 years 56,508 2.19 % 95,806 2.16 % After 3 years but within 4 years 58,492 2.64 % 46,027 1.73 % After 4 years but within 5 years 29,759 2.58 % 71,556 2.57 % 5+ Years 401 2.19 % 20 1.98 % Total certificate of deposit accounts 2,021,642 2.26 % 1,789,165 1.58 % Total deposits $ 5,830,072 1.17 % $ 5,454,044 0.92 % Certificate of deposit accounts issued in amounts of $250,000 or more totaled $557.5 million and $480.8 million as of December 31, 2019 and 2018 , respectively. Interest expense on deposit balances is summarized as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Interest-bearing deposits: NOW accounts $ 436 $ 283 $ 225 Savings accounts 2,900 1,804 1,297 Money market accounts 21,206 15,369 8,863 Certificate of deposit accounts 45,073 24,522 12,903 Total interest-bearing deposits $ 69,615 $ 41,978 $ 23,288 Related Party Deposits Deposit accounts of directors, executive officers and their affiliates totaled $70.4 million and $59.8 million as of December 31, 2019 and 2018 , respectively. Collateral Pledged to Deposits As of December 31, 2019 and 2018 , $184.0 million and $211.5 million , respectively, of collateral was pledged for municipal deposits and TT&L.

Borrowed Funds

Borrowed Funds	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Borrowed Funds	Borrowed Funds Borrowed funds are comprised of the following: At December 31, 2019 2018 (In Thousands) Advances from the FHLBB $ 758,469 $ 784,375 Subordinated debentures and notes 83,591 83,433 Other borrowed funds 60,689 52,734 Total borrowed funds $ 902,749 $ 920,542 Interest expense on borrowed funds for the periods indicated is as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Advances from the FHLBB $ 18,701 $ 18,650 $ 11,330 Subordinated debentures and notes 5,206 5,181 5,081 Other borrowed funds 804 385 170 Total interest expense on borrowed funds $ 24,711 $ 24,216 $ 16,581 Collateral Pledged to Borrowed Funds As of December 31, 2019 and 2018 , $2.5 billion and $2.4 billion , respectively, of investment securities and loans and leases, were pledged as collateral for repurchase agreements, swap agreements, FHLBB borrowings, and municipal deposits and TT&L. The Banks did not have any outstanding FRB borrowings as of December 31, 2019 and 2018 . FHLBB Advances FHLBB advances mature as follows: At December 31, 2019 2018 Amount Callable Amount Weighted Average Rate Amount Callable Amount Weighted Average Rate (Dollars in Thousands) Within 1 year $ 599,262 $ — 2.27 % $ 603,590 $ — 2.19 % Over 1 year to 2 years 139,762 — 2.12 % 160,073 — 2.64 % Over 2 years to 3 years 3,210 — 0.01 % 580 — 3.07 % Over 3 years to 4 years — — — % 3,214 — 0.03 % Over 4 years to 5 years 4,025 — 3.91 % — — — % Over 5 years 12,210 — 3.28 % 16,918 — 3.45 % $ 758,469 $ — 2.26 % $ 784,375 $ — 2.30 % Actual maturities of the advances may differ from those presented above since the FHLBB has the right to call certain advances prior to the scheduled maturity. The FHLBB advances are secured by blanket pledge agreements which require the Banks to maintain certain qualifying assets as collateral. The Banks did not have any FRB borrowings as of December 31, 2019 . Total available borrowing capacity for advances from the FHLBB and FRB was $2.2 billion as of December 31, 2019 for the Banks. The total amount of qualifying collateral for FHLBB and FRB borrowings was $3.5 billion as of December 31, 2019 . Other Borrowed Funds Information concerning other borrowed funds is as follows for the periods indicated below: Year Ended December 31, 2019 2018 (Dollars In Thousands) Outstanding at end of year $ 60,689 $ 52,734 Average outstanding for the year 79,276 46,079 Maximum outstanding at any month-end 122,776 55,144 Weighted average rate at end of year 0.60 % 0.16 % Weighted average rate paid for the year 1.01 % 0.83 % In addition to advances from the FHLBB and subordinated debentures and notes, the Company utilizes other funding sources as part of the overall liquidity strategy. Those funding sources include repurchase agreements, committed and uncommitted lines of credit with several financial institutions. The Company periodically enters into repurchase agreements with its larger deposit and commercial customers as part of its cash management services which are typically overnight borrowings. Repurchase agreements with customers decreased $10.0 million to $42.7 million as of December 31, 2019 from $52.7 million as of December 31, 2018 . The Company has access to a $12.0 million committed line of credit as of December 31, 2019 . As of December 31, 2019 and December 31, 2018 , the Company did not have any borrowings on this committed line of credit outstanding. The Banks also have access to funding through several uncommitted lines of credit of $475.0 million . As of December 31, 2019 , the Company had $18.0 million borrowings on outstanding uncommitted lines of credit as compared to December 31, 2018 , when the Company had no borrowings on outstanding uncommitted lines of credit. Subordinated Debentures and Notes On September 15, 2014, the Company issued $75.0 million of 6.0% fixed-to-floating subordinated notes due September 15, 2029. The Company is obligated to pay 6.0% interest semiannually between September 2014 and September 2024. Subsequently, the Company is obligated to pay 3-month LIBOR plus 3.315% quarterly until the notes mature in September 2029. The following table summarizes the Company's subordinated debentures and notes at the dates indicated. Carrying Amount Issue Date Rate Maturity Date Next Call Date December 31, 2019 December 31, 2018 (Dollars in Thousands) June 26, 2003 Variable; 3-month LIBOR + 3.10% June 26, 2033 March 25, 2020 $ 4,826 $ 4,803 March 17, 2004 Variable; 3-month LIBOR + 2.79% March 17, 2034 March 16, 2020 4,739 4,704 September 15, 2014 6.0% Fixed-to-Variable; 3-month LIBOR + 3.315% September 15, 2029 September 15, 2024 74,026 73,926 Total $ 83,591 $ 83,433 The above carrying amounts of the acquired subordinated debentures included $0.4 million of accretion adjustments and $1.0 million of capitalized debt issuance costs as of December 31, 2019 . This compares to $0.5 million of accretion adjustments and $1.1 million of capitalized debt issuance costs as of December 31, 2018 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Commitments and Contingencies	Commitments and Contingencies Off-Balance Sheet Financial Instruments The Company is party to off-balance sheet financial instruments in the normal course of business to meet the financing needs of its customers and to reduce its own exposure to fluctuations in interest rates. These financial instruments include loan commitments, standby and commercial letters of credits, and loan level derivatives. According to GAAP, these financial instruments are not recorded in the financial statements until they are funded or related fees are incurred or received. The contract amounts reflect the extent of the involvement the Company has in particular classes of these instruments. Such commitments involve, to varying degrees, elements of credit risk and interest-rate risk in excess of the amount recognized in the consolidated balance sheets. The Company's exposure to credit loss in the event of non-performance by the counterparty is represented by the fair value of the instruments. The Company uses the same policies in making commitments and conditional obligations as it does for on-balance sheet instruments. Financial instruments with off-balance-sheet risk at the dates indicated follow: At December 31, 2019 2018 (In Thousands) Financial instruments whose contract amounts represent credit risk: Commitments to originate loans and leases: Commercial real estate $ 50,034 $ 76,642 Commercial 78,058 75,713 Residential mortgage 25,998 16,363 Unadvanced portion of loans and leases 808,681 707,997 Unused lines of credit: Home equity 528,251 487,476 Other consumer 25,374 50,404 Other commercial 380 347 Unused letters of credit: Financial standby letters of credit 10,166 11,491 Performance standby letters of credit 4,652 3,075 Commercial and similar letters of credit 3,823 4,573 Loan level derivatives: Receive fixed, pay variable 1,101,193 714,500 Pay fixed, receive variable 1,101,193 714,500 Risk participation-out agreements 235,693 100,531 Risk participation-in agreements 55,281 35,838 Foreign exchange contracts: Buys foreign currency, sells U.S. currency 1,125 6,573 Sells foreign currency, buys U.S. currency 1,230 6,582 Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require the payment of a fee by the customer. Since some of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer's creditworthiness on a case-by-case basis. The amount of collateral obtained, if any, is based on management's credit evaluation of the borrower. Standby and commercial letters of credits are conditional commitments issued by the Company to guarantee performance of a customer to a third party. These standby and commercial letters of credit are primarily issued to support the financing needs of the Company's commercial customers. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loans to customers. The liability for unfunded credit commitments, which is included in other liabilities, was $1.9 million and $1.9 million as of December 31, 2019 and December 31, 2018 , respectively. From time to time, the Company enters into loan level derivatives, risk participation agreements or foreign exchange contracts with commercial customers and third-party financial institutions. These derivatives allow the Company to offer long-term fixed-rate commercial loans while mitigating the interest-rate or foreign exchange risk of holding those loans. In a loan level derivative transaction, the Company lends to a commercial customer on a floating-rate basis and then enters into an loan level derivative with that customer. Concurrently, the Company enters into offsetting swaps with a third-party financial institution, effectively minimizing its net interest-rate risk exposure resulting from such transactions. The fair value of derivative assets and liabilities was $60.6 million and $59.7 million , respectively, as of December 31, 2019. The fair value of derivative assets and liabilities was $22.5 million and $22.2 million , respectively, as of December 31, 2018. Lease Commitments The Company leases certain office space under various noncancellable operating leases. These leases have original terms ranging from 3 years to over 25 years . Certain leases contain renewal options and escalation clauses which can increase rental expenses based principally on the consumer price index and fair market rental value provisions. The Company considered the following criteria when determining whether a contract contains a lease, the existence of an identifiable asset and the right to obtain substantially all of the economic benefits from use of the asset through the period. The Company used the FHLB classic advance rates as of December 31, 2019 as the discount rate to determine the net present value of the remaining lease payments. At December 31, 2019 (In Thousands) The components of lease expense were as follow: Operating lease cost $ 6,461 Supplemental cash flow information related to leases was as follows: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 6,515 Right-of-use assets obtained in exchange for new lease obligations: Operating leases $ 66 Supplemental balance sheet information related to leases was as follows: Operating Leases Operating lease right-of-use assets $ 24,876 Operating lease liabilities 24,876 Weighted Average Remaining Lease Term Operating leases 7.47 Weighted Average Discount Rate Operating leases 3.2 % A summary of future minimum rental payments under such leases at the dates indicated follows: Year ended December 31, Minimum Rental Payments (In Thousands) 2020 $ 5,886 2021 5,267 2022 4,577 2023 3,672 2024 2,305 Thereafter 6,163 Total $ 27,870 Less imputed interest (2,994 ) $ 24,876 Certain leases contain escalation clauses for real estate taxes and other expenditures, which are not included above. Total rental expense was $6.2 million in 2019 . This compares to total rent expense of $5.8 million in 2018 . In 2017 , total rent expense was $5.5 million . The increase in expense was due to the addition of two banking offices in Wakefield and Braintree, Massachusetts, and a rent increase for the Eastern Funding main office. A portion of the Company's headquarters was rented to third-party tenants which generated rental income of $0.4 million in 2019 , 2018 and 2017 respectively. Rental income was reported in non-interest income in the Company's consolidated statements of income. Legal Proceedings In the normal course of business, there are various outstanding legal proceedings. In the opinion of management, after consulting with legal counsel, the consolidated financial position and results of operations of the Company are not expected to be affected materially by the outcome of such proceedings.

Earnings per Share (EPS)

Earnings per Share (EPS)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings per Share (EPS)	Earnings per Share ("EPS") The following table is a reconciliation of basic EPS and diluted EPS: For the year ended December 31, 2019 2018 2017 Basic Fully Diluted Basic Fully Diluted Basic Fully Diluted (Dollars in Thousands, Except Per Share Amounts) Numerator: Net income $ 87,717 $ 87,717 $ 83,062 $ 83,062 $ 50,518 $ 50,518 Denominator: Weighted average shares outstanding 79,679,781 79,679,781 79,669,668 79,669,668 74,459,508 74,459,508 Effect of dilutive securities — 177,140 — 239,583 — 351,900 Adjusted weighted average shares outstanding 79,679,781 79,856,921 79,669,668 79,909,251 74,459,508 74,811,408 EPS $ 1.10 $ 1.10 $ 1.04 $ 1.04 $ 0.68 $ 0.68

Comprehensive Income_(Loss)

Comprehensive Income/(Loss)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Comprehensive Income/(Loss)	Comprehensive Income/(Loss) Comprehensive income (loss) represents the sum of net income (loss) and other comprehensive income (loss). For the years ended December 31, 2019 , 2018 and 2017 , the Company’s other comprehensive income (loss) include the following two components: (i) unrealized holding losses on investment securities available-for-sale; and (ii) adjustment of accumulated obligation for postretirement benefits. Changes in accumulated other comprehensive income (loss) by component, net of tax, were as follows for the periods indicated: Year Ended December 31, 2019 Investment Securities Available-for-Sale Postretirement Benefits Accumulated Other Comprehensive Income (Loss) (In Thousands) Balance at December 31, 2018 $ (9,712 ) $ 252 $ (9,460 ) Other comprehensive income (loss) 11,911 (168 ) 11,743 Balance at December 31, 2019 $ 2,199 $ 84 $ 2,283 Year Ended December 31, 2018 Investment Securities Available-for-Sale Postretirement Benefits Accumulated Other Comprehensive Loss (In Thousands) Balance at December 31, 2017 $ (6,113 ) $ 163 $ (5,950 ) Other comprehensive (loss) income (3,599 ) 89 (3,510 ) Reclassification due to adoption of ASU 2018-02 — — — Balance at December 31, 2018 $ (9,712 ) $ 252 $ (9,460 ) Year Ended December 31, 2017 Investment Securities Available-for-Sale Postretirement Benefits Accumulated Other Comprehensive Loss (In Thousands) Balance at December 31, 2016 $ (4,213 ) $ 395 $ (3,818 ) Other comprehensive loss (817 ) (252 ) (1,069 ) Reclassification due to adoption of ASU 2018-02 (1,083 ) 20 (1,063 ) Balance at December 31, 2017 $ (6,113 ) $ 163 $ (5,950 )

Derivatives and Hedging Activit

Derivatives and Hedging Activities	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	Derivatives and Hedging Activities The Company utilizes loan level derivatives which consist of interest-rate contracts (swaps, caps and floors), and risk participation agreements as part of the Company's interest-rate risk management strategy for certain assets and liabilities and not for speculative purposes. Based on the Company's intended use for the loan level derivatives at inception, the Company designates the derivative as either an economic hedge of an asset or liability, or a hedging instrument subject to the hedge accounting provisions of FASB ASC Topic 815, "Derivatives and Hedging". Interest-rate swap, cap and floor agreements are entered into as hedges against future interest-rate fluctuations on specifically identified assets or liabilities. The Company did not have derivative fair value hedges or derivative cash flow hedges as of December 31, 2019 or 2018 . Derivatives not designated as hedges are not speculative, but rather, result from a service the Company provides to certain customers for a fee. The Company executes loan level derivative products such as interest-rate swap agreements with commercial banking customers to aid them in managing their interest-rate risk. The interest-rate swap contracts allow the commercial banking customers to convert floating-rate loan payments to fixed-rate loan payments. The Company concurrently enters into offsetting swaps with a third party financial institution, effectively minimizing its net risk exposure resulting from such transactions. The third-party financial institution exchanges the customer's fixed-rate loan payments for floating-rate loan payments. As the interest-rate swap agreements associated with this program do not meet hedge accounting requirements, changes in the fair value are recognized directly in earnings. The Company utilizes risk participation agreements with other banks participating in commercial loan arrangements. Participating banks guarantee the performance on borrower-related interest rate swap contracts. Risk participation agreements are derivative financial instruments and are recorded at fair value. These derivatives are not designated as hedges and therefore, changes in fair value are recorded directly through earnings at each reporting period. The risk participation-out agreements have grown in tandem with the Company's increase in derivative activity. Under a risk participation-out agreement, a derivative asset, the Company participates out a portion of the credit risk associated with the interest rate swap position executed with the commercial borrower, for a fee paid to the participating bank. Under a risk participation-in agreement, a derivative liability, the Company assumes, or participates in, a portion of the credit risk associated with the interest rate swap position with the commercial borrower, for a fee received from the other bank. The Company offers foreign exchange contracts to commercial borrowers to accommodate their business needs. These foreign exchange contracts do not qualify as hedges for accounting purposes. To mitigate the market and liquidity risk associated with these foreign exchange contracts, the Company enters into similar offsetting positions. Asset derivatives and liability derivatives are included in other assets and accrued expenses and other liabilities, respectively on the consolidated balance sheets. The following tables presents the Company's customer related derivative positions for the periods indicated below for those derivatives not designated as hedging. Notional Amount Maturing Number of Positions Less than 1 year Less than 2 years Less than 3 years Less than 4 years Thereafter Total Fair Value December 31, 2019 (Dollars In Thousands) Loan level derivatives Receive fixed, pay variable 119 $ 24,777 $ — $ 31,131 $ 16,794 $ 1,028,491 $ 1,101,193 $ 58,102 Pay fixed, receive variable 119 24,777 — 31,131 16,794 1,028,491 1,101,193 58,102 Risk participation-out agreements 40 13,967 — — 7,143 214,583 235,693 1,229 Risk participation-in agreements 7 — — — 19,000 36,281 55,281 283 Foreign exchange contracts Buys foreign currency, sells U.S. currency 16 $ 1,125 $ — $ — $ — $ — $ 1,125 $ 54 Sells foreign currency, buys U.S. currency 18 1,230 — — — — 1,230 53 Notional Amount Maturing Number of Positions Less than 1 year Less than 2 years Less than 3 years Less than 4 years Thereafter Total Fair Value December 31, 2018 (Dollars In Thousands) Loan level derivatives Receive fixed, pay variable 86 $ 1,931 $ 26,419 $ — $ 31,762 $ 654,388 $ 714,500 $ 6,081 Pay fixed, receive variable 86 1,931 26,419 — 31,762 654,388 714,500 6,081 Risk participation-out agreements 26 — 14,892 — — 85,639 100,531 344 Risk participation-in agreements 5 — — — — 35,838 35,838 84 Foreign exchange contracts Buys foreign currency, sells U.S. currency 22 $ 6,573 $ — $ — $ — $ — $ 6,573 $ 123 Sells foreign currency, buys U.S. currency 37 6,582 — — — — 6,582 131 Changes in the fair value are recognized directly in the Company's consolidated statements of income and are included in other non-interest income in the consolidated statements of income. The table below presents the net gain (loss) recognized in income due to changes in the fair value for the year ended December 31, 2019 and 2018 . Year Ended December 31, 2019 2018 (In Thousands) Net gain recognized in income on: Net risk participation agreements 686 205 Foreign exchange contracts (7 ) 1 Total $ 679 $ 206 By using derivative financial instruments, the Company exposes itself to credit risk which is the risk of failure by the counterparty to perform under the terms of the derivative contract. When the fair value of a derivative contract is positive, the counterparty owes the Company, which creates credit risk for the Company. When the fair value of a derivative is negative, the Company owes the counterparty and, therefore, it does not possess credit risk. The credit risk in derivative instruments is mitigated by entering into transactions with highly-rated counterparties that management believes to be creditworthy and by limiting the amount of exposure to each counterparty by either cross collateralizing the underlying hedged loan or through bilateral posting of collateral to cover exposure. As the swaps are subject to master netting agreements, the Company had limited exposure relating to loan level derivatives with institutional counterparties as of December 31, 2019 and 2018 . The estimated net credit risk exposure for derivative financial instruments was zero as of December 31, 2019 , and 2018 . Certain derivative agreements contain provisions that require the Company to post collateral if the derivative exposure exceeds a threshold amount. The Company posted collateral of $86.5 million and $5.9 million in the normal course of business as of December 31, 2019 and 2018 , respectively. The tables below present the offsetting of derivatives and amounts subject to master netting agreements not offset in the consolidated balance sheet at the dates indicated. At December 31, 2019 Gross Gross Amounts Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Gross Amounts Not Offset in the Statement of Financial Position Net Amount Financial Instruments Pledged Cash Collateral Pledged (In Thousands) Asset derivatives Loan level derivatives $ 59,365 $ — $ 59,365 $ — $ 11,900 $ 47,465 Risk participation-out agreements 1,229 — 1,229 — — 1,229 Foreign exchange contracts 54 — 54 — — 54 Total $ 60,648 $ — $ 60,648 $ — $ 11,900 $ 48,748 Liability derivatives Loan level derivatives $ 59,365 $ — $ 59,365 $ 86,521 $ — $ (27,156 ) Risk participation-in agreements 283 — 283 — — 283 Foreign exchange contracts 53 — 53 — — 53 Total $ 59,701 $ — $ 59,701 $ 86,521 $ — $ (26,820 ) At December 31, 2018 Gross Gross Amounts Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Gross Amounts Not Offset in the Statement of Financial Position Net Amount Financial Instruments Pledged Cash Collateral Pledged (In Thousands) Asset derivatives Loan level derivatives $ 22,013 $ — $ 22,013 $ — $ 50 $ 21,963 Risk participation-out agreements 344 — 344 — — 344 Foreign exchange contracts 131 — 131 — — 131 Total $ 22,488 $ — $ 22,488 $ — $ 50 $ 22,438 Liability derivatives Loan level derivatives $ 22,013 $ — $ 22,013 $ 5,877 $ — $ 16,136 Risk participation-in agreements 84 — 84 — — 84 Foreign exchange contracts 123 — 123 — — 123 Total $ 22,220 $ — $ 22,220 $ 5,877 $ — $ 16,343 The Company has agreements with certain of its derivative counterparties that contain credit-risk-related contingent provisions. These provisions provide the counterparty with the right to terminate its derivative positions and require the Company to settle its obligations under the agreements if the Company defaults on certain of its indebtedness or if the Company fails to maintain its status as a well-capitalized institution.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense is comprised of the following amounts: Year Ended December 31, 2019 2018 2017 (In Thousands) Current provision: Federal $ 21,706 $ 23,949 $ 27,825 State 6,565 7,693 5,013 Total current provision 28,271 31,642 32,838 Deferred provision (benefit): Federal 701 (4,323 ) 10,209 State (703 ) (1,130 ) 589 Total deferred provision (benefit) (2 ) (5,453 ) 10,798 Total provision for income taxes $ 28,269 $ 26,189 $ 43,636 Total provision for income taxes differed from the amounts computed by applying the statutory U.S. federal income tax rate of 21.0% in 2019 , 21.0% in 2018 and 35.0% in 2017 to income before tax expense as a result of the following: Year Ended December 31, 2019 2018 2017 (Dollars In Thousands) Expected income tax expense at statutory federal tax rate $ 24,366 $ 23,675 $ 34,039 State taxes, net of federal income tax benefit 4,837 5,184 3,641 Bank-owned life insurance (216 ) (218 ) (364 ) Tax-exempt interest income (435 ) (487 ) (873 ) Income attributable to noncontrolling interest in subsidiary (11 ) (933 ) (870 ) Merger and acquisition expense — 32 138 Tax Act Adjustment — (707 ) 8,965 Investments in affordable housing projects (369 ) (358 ) (653 ) Other, net 97 1 (387 ) Total provision for income taxes $ 28,269 $ 26,189 $ 43,636 Effective income tax rate 24.4 % 23.2 % 44.9 % The Company's effective tax rate was 24.4% as of December 31, 2019 compared to 23.2% as of December 31, 2018 . The Company's expected income tax expense was $0.7 million higher in 2019. The item impacting the Company's increase in the effective tax rate from 2018 involved Brookline Bank's completed purchase of the remaining interest in Eastern Funding in 2019. Tax savings of approximately $0.9 million were recognized for this portion of Eastern Funding in 2018, but not in 2019. In 2018, the Company made an adjustment related to the Tax Act that reduced the provision for income taxes by $0.7 million . On December 22, 2017, the Tax Act was enacted, which represents the most comprehensive reform to the U.S. tax code in over thirty years. The majority of the provisions of the Tax Act took effect on January 1, 2018. The Tax Act lowered the Company’s federal tax rate from 35% to 21%. The Tax Act also contains other provisions that may affect the Company currently or in future years. Among these are changes to the deductibility of meals and entertainment, the deductibility of executive compensation, accelerated expensing of depreciable property for assets placed in service after September 27, 2017 and before 2023, limits the deductibility of net interest expense, eliminated the corporate alternative minimum tax, limited net operating loss carryforwards to 80% of taxable income and a parking disallowance related to employee parking. As a result of the Tax Act, in 2017, management re-valued the carrying value of our net deferred tax asset and investments in low income housing tax credits. The impact of the Tax Act resulted in a write down of the carrying balance of net deferred tax assets and investments in affordable housing projects of $8.6 million and $0.3 million , respectively. The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities at the dates indicated are as follows: At December 31, 2019 2018 (In Thousands) Deferred tax assets: Allowance for loan and lease losses $ 16,294 $ 15,936 Right-of-use asset - operating leases 6,450 — Deferred compensation 4,748 4,692 Identified intangible assets and goodwill 4,319 — Supplemental Executive Retirement Plans 3,023 2,846 Unrealized loss on investment securities available-for-sale — 2,737 Net operating loss carryforwards 187 976 Postretirement benefits 458 391 Nonaccrual interest 557 482 Accrued expense — 372 Restricted stock and stock option plans 751 497 Employee stock ownership plan 83 106 Other 733 331 Total gross deferred tax assets 37,603 29,366 Deferred tax liabilities: Operating leases - liability 6,450 — Identified intangible assets and goodwill — 2,428 Deferred loan origination costs, net 3,785 3,537 Depreciation 420 789 Unrealized gain on investment securities available-for-sale 622 — Prepaid expense 110 116 Accrued Expense 122 — Acquisition fair value adjustments 1,077 1,001 Total gross deferred tax liabilities 12,586 7,871 Net deferred tax asset $ 25,017 $ 21,495 As of December 31, 2019 , the Company had net operating loss carryforwards for federal income tax purposes of $0.9 million gross which are available to offset future federal taxable income, if any, through 2020. Of this total net operating loss carryforward amount, $0.7 million is related to the Company's First Commons Bank transaction. The Company has determined that a valuation allowance is not required for any of its deferred tax assets because it believes that it is more likely than not that these assets will reverse against future taxable income. For federal income tax purposes, the Company has a $1.8 million reserve for credit losses which remains subject to recapture. If any portion of the reserve is used for purposes other than to absorb the losses for which it was established, approximately 150% of the amount actually used (limited to the amount of the reserve) would be subject to taxation in the year in which used. As the Company intends to use the reserve only to absorb credit losses, no provision has been made for the $0.5 million liability that would result if 100% of the reserve were recaptured. The Company did not have any unrecognized tax benefits accrued as income tax payables, receivables or as deferred tax items as of December 31, 2019 and 2018 . The Company files U.S. federal and state income tax returns. As of December 31, 2019 , the Company is subject to examination by the Massachusetts, Rhode Island and several other state tax authorities for tax years after December 31, 2014

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Preferred Stock The Company is authorized to issue 50,000,000 shares of serial preferred stock, par value $0.01 per share, from time to time in one or more series subject to limitations of law. The Board of Directors is authorized to fix the designations, powers, preferences, limitations and rights of the shares of each such series. As of December 31, 2019 , there were no shares of preferred stock issued. Capital Distributions and Restrictions Thereon The Company is a legal entity separate and distinct from each of the Banks and Brookline Securities Corp. The Company's primary source of revenue is dividends paid to it by the Banks and Brookline Securities Corp. The FRB has authority to prohibit the Company from paying dividends to the Company's shareholders if such payment is deemed to be an unsafe or unsound practice. The FRB has indicated generally that it may be an unsafe or unsound practice for bank holding companies to pay dividends unless the bank holding company's net income over the preceding year is sufficient to fund the dividends and the expected rate of earnings retention is consistent with the organization's capital needs, asset quality and overall financial condition. The FRB also has the authority to use its enforcement powers to prohibit the Banks from paying dividends to the Company if, in its opinion, the payment of dividends would constitute an unsafe or unsound practice. Federal law also prohibits the payment of dividends by a bank that will result in the bank failing to meet its applicable capital requirements on a pro forma basis. In addition, a state bank that is a member of the Federal Reserve System may not declare or pay a dividend if the total of all dividends declared during the calendar year, including the proposed dividend, exceeds the sum of the bank's net income (as reportable in its Reports of Condition and Income) during the current calendar year and the retained net income of the prior two calendar years, unless the dividend has been approved by the FRB. Payment of dividends by a bank is also restricted pursuant to various state regulatory limitations, including the Massachusetts Division of Banks in the case of Brookline Bank and the Banking Division of the Rhode Island Department of Business Regulation in the case of BankRI. Common Stock Repurchases On February 4, 2016, the Company's Board of Directors authorized a stock repurchase program to acquire up to $10.0 million of the Company's common stock over a period of twelve months ending on January 31, 2017 (the "2016 Stock Repurchase Plan"). No shares were purchased under the 2016 Stock Repurchase Plan. On December 5, 2018, the Company’s Board of Directors authorized a stock repurchase program to acquire up to $10.0 million of the Company’s common stock over a period of twelve months ending on December 31, 2019 (the “2018 Stock Repurchase Plan”). As of December 31, 2018 , 725,583 shares of the Company's common stock were repurchased under the 2018 Stock Repurchase Plan. On January 30, 2019, the Company’s Board of Directors authorized a stock repurchase program to acquire up to $10.0 million of the Company’s common stock over a period of eleven months ending on December 31, 2019 (the “2019 Stock Repurchase Plan”). As of December 31, 2019 , 103,758 shares of the Company’s common stock were repurchased under the 2019 Stock Repurchase Plan. On December 4, 2019, the Company’s Board of Directors authorized a stock repurchase program to acquire up to $10.0 million of the Company’s common stock over a period of twelve months ending on December 31, 2020 (the “2020 Stock Repurchase Plan”). There is no guarantee as to the exact number of shares, if any, to be repurchased by the Company under the 2020 Stock Repurchase Plan. Repurchases may be made from time to time depending on market conditions and other factors, and will be conducted through open market or private transactions, through block trades, and pursuant to any trading plan that may be adopted in accordance with the Securities and Exchange Commission Rule 10b5-1. There is no guarantee as to the exact number of shares, if any, to be repurchased by the Company. Common Stock Issuance On, April 27, 2017, the Company entered into an underwriting agreement with Piper Jaffray & Co., as representative of the underwriters named therein (collectively, the “Underwriters”), to offer and sell 5,175,000 shares of the Company’s common stock, $0.01 par value per share at a public offering price of $14.50 per share in an underwritten public offering (the “Offering”). In conjunction with the Offering, the Company granted the Underwriters a 30-day option to purchase up to an additional 776,250 shares of its common stock. On May 2, 2017, the Company and the Underwriters closed the Offering. The Underwriters exercised their option resulting in a new issuance in the aggregate of 5,951,250 shares of the Company’s common stock at a price to the public of $14.50 per share. The Company received net proceeds of $82.0 million after deductions for underwriting discounts, commissions, and expenses. Restricted Retained Earnings As part of the stock offering in 2002 and as required by regulation, Brookline Bank established a liquidation account for the benefit of eligible account holders and supplemental eligible account holders who maintain their deposit accounts at Brookline Bank after the stock offering. In the unlikely event of a complete liquidation of Brookline Bank (and only in that event), eligible depositors who continue to maintain deposit accounts at Brookline Bank shall be entitled to receive a distribution from the liquidation account. Accordingly, retained earnings of the Company are deemed to be restricted up to the balance of the liquidation account. The liquidation account balance is reduced annually to the extent that eligible depositors have reduced their qualifying deposits as of each anniversary date. Subsequent increases in deposit account balances do not restore an account holder's interest in the liquidation account. The liquidation account totaled $11.9 million (unaudited), $13.0 million (unaudited), and $15.1 million (unaudited) at December 31, 2019 , 2018 and 2017 , respectively.

Regulatory Capital Requirements

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Regulatory Capital Requirements	Regulatory Capital Requirements The Company's primary source of cash is dividends from the Banks and Brookline Securities Corp. The Banks are subject to certain restrictions on the amount of dividends that they may declare without prior regulatory approval. In addition, the dividends declared cannot be in excess of the amount which would cause the Banks to fall below the minimum required for capital adequacy purposes. The Company is a bank holding company within the meaning of the Bank Holding Company Act of 1956, as amended (the "BHCA") and as such, must comply with the capital requirements of the FRB at the consolidated level. As member banks of the FRB, Brookline Bank and BankRI are also required to comply with the regulatory capital requirement of the FRB. The FRB has promulgated regulations imposing minimum capital requirements for bank holding companies and state member banks as well as prompt corrective action regulations for state member banks that implement the system of prompt corrective action established by Section 38 of the Federal Deposit Insurance Act, as amended (the "FDIA"). Under the prompt corrective action regulations in effect as of December 31, 2019 , a bank is "well-capitalized" if it has: (1) a total risk-based capital ratio of 10.0% or greater; (2) a Tier 1 risk-based capital ratio of 8.0% or greater; (3) a common equity Tier 1 capital ratio of 6.5% or greater; (4) a Tier 1 leverage ratio of 5.0% or greater; and (5) is not subject to any written agreement, order, capital directive or prompt corrective action directive to meet and maintain a specific capital level for any capital measure. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company's financial statements. Under capital adequacy guidelines, the Company and each of the Banks must meet specific capital guidelines that involve quantitative measures of the Company's and the Banks' assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. In addition, the prompt corrective action rules applicable to state member banks establish a framework of supervisory actions for state member banks that are not at least adequately capitalized. The Company's and the Banks' capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. Prompt corrective action provisions are not applicable to bank holding companies. Bank holding companies are not subject to prompt corrective action requirements. However, a bank holding company is considered "well capitalized" for purpose of the FRB's Regulation Y (which can affect eligibility for expedited application processes to make acquisitions and engage in new activities) if the bank holding company maintains on a consolidated basis a total risk-based capital ratio of 10.0% or greater and a Tier 1 risk-based capital ratio of 6.0% or greater and is not subject to any written agreement under capital directive or prompt correction action directive issued by the FRB to meet and maintain a specific capital level for any capital measure. Beginning January 1, 2019 , the Company and the Banks will have to maintain a capital conservation buffer composed of Common Equity Tier 1 capital equal to 2.5% of risk-weighted assets above the amounts required to be adequately capitalized in order to avoid limitations on capital distributions, including dividend payments and certain discretionary bonus payments to executive officers. Capital ratios required to be considered well-capitalized exceed the ratios required under the capital conservation buffer requirement at December 31, 2019 . As of December 31, 2019 , the Company and the Banks are each under the primary regulation of, and must comply with, the capital requirements of the FRB. As of December 31, 2019 , the Company and the Banks exceeded all regulatory capital requirements and were considered “well-capitalized” under prompt corrective action regulations, as amended to reflect the changes under Basel III Capital Rules. The following table presents actual and required capital ratios as of December 31, 2019 for the Company and the Banks under the Basel III Capital Rules based on the phase-in provision of the Basel III Capital Rules and the minimum required capital levels as of January 1, 2019 when the Basel III Capital Rules have been fully phased in. Actual Minimum Required for Capital Adequacy Purposes Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer Minimum Required to be Considered “Well-Capitalized” Under Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in Thousands) At December 31, 2019: Brookline Bancorp, Inc. Common equity Tier 1 capital ratio (1) $ 780,962 11.44 % $ 307,197 4.50 % $ 477,861 7.00 % N/A N/A Tier 1 leverage capital ratio (2) 790,527 10.28 % 307,598 4.00 % 307,598 4.00 % N/A N/A Tier 1 risk-based capital ratio (3) 790,527 11.58 % 409,599 6.00 % 580,266 8.50 % N/A N/A Total risk-based capital ratio (4) 927,515 13.59 % 545,999 8.00 % 716,623 10.50 % N/A N/A Brookline Bank Common equity Tier 1 capital ratio (1) $ 513,311 11.44 % $ 201,914 4.50 % $ 314,089 7.00 % $ 291,654 6.50 % Tier 1 leverage capital ratio (2) 513,311 10.42 % 197,048 4.00 % 197,048 4.00 % 246,310 5.00 % Tier 1 risk-based capital ratio (3) 513,311 11.44 % 269,219 6.00 % 381,394 8.50 % 358,959 8.00 % Total risk-based capital ratio (4) 555,474 12.38 % 358,949 8.00 % 471,121 10.50 % 448,687 10.00 % BankRI Common equity Tier 1 capital ratio (1) $ 240,362 11.75 % $ 92,054 4.50 % $ 143,194 7.00 % $ 132,966 6.50 % Tier 1 leverage capital ratio (2) 240,362 9.97 % 96,434 4.00 % 96,434 4.00 % 120,543 5.00 % Tier 1 risk-based capital ratio (3) 240,362 11.75 % 122,738 6.00 % 173,879 8.50 % 163,651 8.00 % Total risk-based capital ratio (4) 258,719 12.65 % 163,617 8.00 % 214,747 10.50 % 204,521 10.00 % First Ipswich Common equity Tier 1 capital ratio (1) $ 41,320 13.45 % $ 13,825 4.50 % $ 21,505 7.00 % $ 19,969 6.50 % Tier 1 leverage capital ratio (2) 41,320 8.80 % 18,782 4.00 % 18,782 4.00 % 23,477 5.00 % Tier 1 risk-based capital ratio (3) 41,320 13.45 % 18,433 6.00 % 26,113 8.50 % 24,577 8.00 % Total risk-based capital ratio (4) 43,762 14.24 % 24,585 8.00 % 32,268 10.50 % 30,732 10.00 % _______________________________________________________________________________ (1) Common equity Tier 1 capital ratio is calculated by dividing common equity Tier 1 capital by risk-weighted assets. The ratio was established as part of the implementation of Basel III, effective January 1, 2015. (2) Tier 1 leverage capital ratio is calculated by dividing Tier 1 capital by average assets. (3) Tier 1 risk-based capital ratio is calculated by dividing Tier 1 capital by risk-weighted assets. (4) Total risk-based capital ratio is calculated by dividing total capital by risk-weighted assets. The following table presents actual and required capital ratios as of December 31, 2018 for the Company and the Banks under the regulatory capital rules then in effect. Actual Minimum Required for Capital Adequacy Purposes Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer Minimum Required to be Considered “Well-Capitalized” Under Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in Thousands) At December 31, 2018: Brookline Bancorp, Inc. Common equity Tier 1 capital ratio (1) $ 745,103 11.94 % $ 280,818 4.50 % $ 436,828 7.00 % N/A N/A Tier 1 leverage capital ratio (2) 765,089 10.58 % 289,259 4.00 % 289,259 4.00 % N/A N/A Tier 1 risk-based capital ratio (3) 765,089 12.26 % 374,432 6.00 % 530,445 8.50 % N/A N/A Total risk-based capital ratio (4) 899,563 14.42 % 499,064 8.00 % 655,022 10.50 % N/A N/A Brookline Bank Common equity Tier 1 capital ratio (1) $ 495,798 12.06 % $ 184,999 4.50 % $ 287,777 7.00 % $ 267,221 6.50 % Tier 1 leverage capital ratio (2) 506,277 11.02 % 183,767 4.00 % 183,767 4.00 % 229,708 5.00 % Tier 1 risk-based capital ratio (3) 506,277 12.32 % 246,563 6.00 % 349,298 8.50 % 328,751 8.00 % Total risk-based capital ratio (4) 545,533 13.27 % 328,882 8.00 % 431,658 10.50 % 411,102 10.00 % BankRI Common equity Tier 1 capital ratio (1) $ 209,670 11.37 % $ 82,983 4.50 % $ 129,084 7.00 % $ 119,864 6.50 % Tier 1 leverage capital ratio (2) 209,670 9.35 % 89,698 4.00 % 89,698 4.00 % 112,123 5.00 % Tier 1 risk-based capital ratio (3) 209,670 11.37 % 110,644 6.00 % 156,745 8.50 % 147,525 8.00 % Total risk-based capital ratio (4) 227,674 12.35 % 147,481 8.00 % 193,569 10.50 % 184,351 10.00 % First Ipswich Common equity Tier 1 capital ratio (1) $ 39,655 13.91 % $ 12,829 4.50 % $ 19,956 7.00 % $ 18,530 6.50 % Tier 1 leverage capital ratio (2) 39,655 9.59 % 16,540 4.00 % 16,540 4.00 % 20,675 5.00 % Tier 1 risk-based capital ratio (3) 39,655 13.91 % 17,105 6.00 % 24,232 8.50 % 22,807 8.00 % Total risk-based capital ratio (4) 42,944 15.06 % 22,812 8.00 % 29,941 10.50 % 28,515 10.00 % _______________________________________________________________________________ (1) Common equity Tier 1 capital ratio is calculated by dividing common equity Tier 1 capital by risk-weighted assets. The ratio was established as part of the implementation of Basel III, effective January 1, 2015. (2) Tier 1 leverage capital ratio is calculated by dividing Tier 1 capital by average assets. (3) Tier 1 risk-based capital ratio is calculated by dividing Tier 1 capital by risk-weighted assets. (4) Total risk-based capital ratio is calculated by dividing total capital by risk-weighted assets.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Postretirement Benefits Postretirement benefits are provided for part of the annual expense of health insurance premiums for certain retired employees and their dependents. No contributions are made by the Company to invest in assets allocated for the purpose of funding this benefit obligation. The following table presents the change in plan assets and change in benefit obligation: Year Ended December 31, 2019 2018 2017 (In Thousands) Change in plan assets: Fair value of plan assets at beginning of year $ — $ — $ — Employer contributions 32 31 19 Benefits paid (32 ) (31 ) (19 ) Fair value of plan assets at end of year $ — $ — $ — Change in benefit obligation: Benefit obligation at beginning of year $ 1,490 $ 1,534 $ 1,135 Service cost 54 70 49 Interest cost 60 59 43 Estimated benefits paid (32 ) (31 ) (19 ) Actuarial loss (gain) 185 (142 ) 326 Benefit obligation at end of year $ 1,757 $ 1,490 $ 1,534 Funded status at end of year $ 1,757 $ 1,490 $ 1,534 Accumulated benefit obligation at end of year $ 1,757 $ 1,490 $ 1,534 The liability for the postretirement benefits included in accrued expenses and other liabilities was $1.8 million , $1.5 million , and $1.5 million as of December 31, 2019 , 2018 and 2017 , respectively. The following table presents the components of net periodic postretirement benefit cost and other amounts recognized in other comprehensive income: Year Ended December 31, 2019 2018 2017 (In Thousands) Net periodic benefit expense: Service cost $ 54 $ 70 $ 49 Interest cost 60 59 43 Prior service credit (21 ) (21 ) (21 ) Actuarial gain (27 ) — (47 ) Net periodic benefit expense $ 66 $ 108 $ 24 Changes in postretirement benefit obligation recognized in other comprehensive income: Net actuarial (loss) gain (206 ) $ 142 $ (401 ) Prior service credit (21 ) (21 ) (21 ) Total pre-tax changes in postretirement benefit obligation recognized in other comprehensive income $ (227 ) $ 121 $ (422 ) The discount rate used to determine the actuarial present value of projected postretirement benefit obligations was 3.19% in 2019 , 4.22% in 2018 and 3.62% in 2017 . The estimated prior service credit that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2020 is $100 thousand . The actual health care trend used to measure the accumulated postretirement benefit obligation in 2019 for plan participants below age 65 and for plan participants over age 65 was 13.3% and 1.2% , respectively. In 2018 , the rate for plan participants below age 65 and for plan participants over age 65 was 3.1% and 2.4% , respectively. The health care trend rates for 2018 and 2019 are based on actual changes in medical premium rates for those years. The rates to be used in 2020 through 2024 are expected to be in the range of 5.9% to 5.1% and to decline gradually thereafter to 4.5% . Assumed health care trend rates may have a significant effect on the amounts reported for the postretirement benefit plan. A 1% change in assumed health care cost trend rates would have the following effects: Year Ended 1% Increase 1% Decrease (In Thousands) Effect on total service and interest cost components of net periodic postretirement benefit costs $ 25 $ (20 ) Effect on the accumulated postretirement benefit obligation 365 (289 ) 401(k) Plan The Company administers one 401(k) plan, which is a qualified, tax-exempt profit-sharing plan with a salary deferral feature under Section 401(k) of the Internal Revenue Code. Each employee, excluding temporary employees, who has attained the age of 21 is eligible to participate in the 401(k) plan by making voluntary contributions, subject to certain limits based on federal tax laws. The Company makes a matching contribution of the amount contributed by eligible employees, up to 5% of the employee's yearly compensation. Expenses associated with the plans were $3.1 million in 2019 , $3.2 million in 2018 , and $2.6 million in 2017 . Nonqualified Deferred Compensation Plan The Company also maintains a Nonqualified Deferred Compensation Plan (the "Nonqualified Plan") under which certain participants may contribute the amounts they are precluded from contributing to the Company's 401(k) plan because of the qualified plan limitations, and additional compensation deferrals that may be advantageous for personal income tax or other planning reasons. Expenses associated with the Nonqualified Plan in 2019 , 2018 and 2017 were $236.2 thousand , $181.1 thousand , and $128.5 thousand , respectively. Accrued liabilities associated with the Nonqualified Plan in 2019 , 2018 , and 2017 were $5.5 thousand , $5.5 thousand , and $80.2 thousand , respectively. Supplemental Executive Retirement Agreements The Company acquired two Supplemental Executive Retirement Plans (the "SERPs") as part of its acquisition of BankRI. The Company maintains the SERPs for certain senior executives who are entitled to an annual retirement benefit. As of December 31, 2019 , there were 13 participants in the SERPs. The Company funded a Rabbi Trust to provide a partial funding source for the Company's liabilities under the SERPs. In 2016, a portion of the Company's BOLI assets were transferred into the Rabbi Trust as a replacement for the funds previously held in the Rabbi Trust. The Company records the liability for the SERPs based on an actuarial calculation in accordance with GAAP, and no actuarial gains and losses are recognized. Total expenses for benefits payable under the SERPs for the years ended December 31, 2019 , and 2018 were $1.1 million and $0.5 million , respectively. Aggregate benefits payable included in accrued expenses and other liabilities as of December 31, 2019 and 2018 were $12.8 million and $12.1 million , respectively. The nominal discount rate used to determine the actuarial present value of projected benefits under the agreements was 3.25% and 4.00% in the years 2019 and 2018 , respectively. Employee Stock Ownership Plan Brookline Bank established an Employee Stock Ownership Plan ("ESOP") on November 1, 1997. The Company's ESOP loan to Brookline Bank to purchase 546,986 shares of Company common stock is payable in quarterly installments over 30 years, bears interest at 8.50% per annum, matures December 31, 2021, and can be prepaid without penalty. The loan is repaid to the Company in the form of cash contributions from Brookline Bank, subject to federal tax law limits. The outstanding balance of the loan as of December 31, 2019 and 2018 , was $0.8 million and $1.0 million , respectively, and is eliminated in consolidation. Shares of common stock used as collateral to secure the loan are released and available for allocation to eligible employees as the principal and interest on the loan is paid. The ESOP was amended in 2015 to permit all eligible participants in the ESOP as of July 1, 2015 or any eligible participants after July 1, 2015 to be fully vested in the ESOP upon the date of eligibility. Dividends on released shares are credited to the participants' ESOP accounts. Dividends on unallocated shares of common stock are generally applied towards payment of the loan. ESOP shares committed to be released are considered outstanding in determining earnings per share. As of December 31, 2019 and 2018 , the ESOP held 79,548 and 109,950 unallocated shares, respectively at an aggregate cost of $0.4 million and $0.6 million , respectively. The market value of such shares as of December 31, 2019 and 2018 was $1.3 million and $1.5 million , respectively. Compensation and employee benefits expense related to the ESOP was $0.5 million in 2019 , $0.5 million in 2018 and $0.5 million in 2017 , based on the commitment to release to eligible employees 30,402 shares in 2019 , 32,382 shares in 2018 and 34,356 shares in 2017 . Share-Based Compensation Plans Under the Brookline Bancorp, Inc. 2014 Equity Incentive Plan (the “2014 Plan”), approved by stockholders on May 7, 2014, the Company may award stock options, stock appreciation rights, restricted stock, restricted stock units, unrestricted stock, performance share awards, dividend equivalent rights and cash-based awards to officers, employees, non-employee directors and consultants of the Company. The maximum number of shares that may be issued under the 2014 Plan is 1,750,000 . Under the Brookline Bancorp, Inc. 2011 Restricted Stock Plan (the “2011 Plan”), approved by stockholders on April 20, 2011, the Company may grant shares of restricted stock to employees and directors. The maximum number of shares that may be issued under the 2011 Plan is 500,000 . Of the awarded shares, generally 50% vest ratably over three years with one-third of such shares vesting at each of the first, second and third anniversary dates of the awards. The remaining 50% of each award has a cliff vesting schedule and vest three years after the award date based on the level of the Company's achievement of identified performance targets in comparison to the level of achievement of such identified performance targets by a defined peer group comprised of 17 financial institutions. The specific performance measure targets are approved by annually by the Compensation Committee and are discussed in the Company's Proxy Statement. If a grantee leaves the Company prior to the third anniversary date of an award, any unvested shares are forfeited. Dividends declared with respect to shares awarded will be held by the Company and paid to the grantee only when the shares vest. Shares issued upon vesting may be either authorized but unissued shares or reacquired shares held by the Company as treasury shares. Any shares not issued because vesting requirements are not met will be retired back to treasury and be made available again for issuance under the Plans. Total expense for the 2014 Plan and the 2011 Plan was $2.4 million in 2019 , $2.5 million in 2018 and $2.3 million in 2017 , respectively. Total income tax benefits on vested awards was $0.1 million in 2019 , $1.2 million in 2018 , and $0.7 million in 2017 . Dividends paid on unvested awards under the 2014 Plan and the 2011 Plan, which are recognized as compensation expense, were $0.1 million in 2019 , $0.2 million in 2018 , and $0.1 million in 2017 . The following table presents information about the Company's restricted stock awards as of and for the year ending December 31, 2019 : Restricted Stock Awards Outstanding Weighted Average Price per Share (Dollars in Thousands, Except Per Share Amounts) Restricted Stock Awards: Outstanding at December 31, 2018 390,635 $ 15.21 Granted 212,461 14.25 Vested (175,160 ) 14.46 Forfeited / Canceled (21,486 ) 11.78 Outstanding at December 31, 2019 406,450 $ 15.21 Unrecognized compensation cost $ 3,964 Weighted average remaining recognition period (months) 24 Stock Options Shares issued upon the exercise of a stock option may be either authorized but unissued shares or reacquired shares held by the Company as treasury shares. Any shares subject to an award which expire or are terminated unexercised will again be available for issuance under the plans. The exercise price of options awarded is the fair market value of the common stock of the Company on the date the award is made. Certain of the options include a reload feature whereby an optionee exercising an option by delivery of shares of common stock would automatically be granted an additional option at the fair market value of stock when such additional option is granted equal to the number of shares so delivered. If an individual to whom a stock option was granted ceases to maintain continuous service by reason of normal retirement, death or disability, or following a change in control, all options and rights granted and not fully exercisable become exercisable in full upon the happening of such an event and shall remain exercisable for a period ranging from 3 months to 5 years . No options were granted in 2019 , 2018 , or 2017 . There was no expense for the stock option plans in 2019 , 2018 , and 2017 . The following table presents a summary of the status of the Company's stock options outstanding as of and for the year ending December 31, 2019 : Options Outstanding Weighted Average Exercise Price Per Share Aggregate Intrinsic Value Weighted Average Contractual Term (In Years) (Dollars in Thousands, Except Per Share Amounts) Employee Stock Options (1) : Outstanding at December 31, 2018 5,000 $ 9.90 Granted — — Exercised — — Forfeited / Canceled — — Outstanding at December 31, 2019 5,000 $ 9.90 $ 33 0.8 Exercisable at December 31, 2019 5,000 $ 9.90 $ 33 0.8 _____________________________________________________________________________ (1) Options granted pursuant to the Brookline Bancorp, Inc. 2003 Stock Option Plan (the “2003 Stock Option Plan”). The 2003 Stock Option Plan terminated by its terms on October 16, 2013, however, outstanding option awards granted pursuant to the 2003 Stock Option Plan may be exercised for 10 years

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments A description of the valuation methodologies used for assets and liabilities measured at fair value on a recurring and non-recurring basis, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. There were no changes in the valuation techniques used during 2019 and 2018 . Assets and Liabilities Recorded at Fair Value on a Recurring Basis The following table set forth the carrying value of assets and liabilities measured at fair value on a recurring basis at December 31, 2019 and 2018 : Carrying Value as of December 31, 2019 Level 1 Level 2 Level 3 Total (In Thousands) Assets: Investment securities available-for-sale: Debt securities: GSE debentures $ — $ 185,803 $ — $ 185,803 GSE CMOs — 85,932 — 85,932 GSE MBSs — 153,343 — 153,343 SBA commercial loan asset-backed securities — 34 — 34 Corporate debt obligations — 28,986 — 28,986 U.S. Treasury bonds — 44,897 — 44,897 Total investment securities available-for-sale $ — $ 498,995 $ — $ 498,995 Equity securities held-for-trading $ 2,569 $ 1,012 $ — $ 3,581 Loan level derivatives — 59,365 — 59,365 Risk participation-out agreements — 1,229 — 1,229 Foreign exchange contracts — 54 — 54 Liabilities: Loan level derivatives $ — $ 59,365 $ — $ 59,365 Risk participation-in agreements — 283 — 283 Foreign exchange contracts — 53 — 53 Carrying Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (In Thousands) Assets: Investment securities available-for-sale: Debt securities: GSE debentures $ — $ 181,079 $ — $ 181,079 GSE CMOs — 103,130 — 103,130 GSE MBSs — 165,089 — 165,089 SBA commercial loan asset-backed securities — 51 — 51 Corporate debt obligations — 39,708 — 39,708 U.S. Treasury bonds — 13,736 — 13,736 Total investment securities available-for-sale $ — $ 502,793 $ — $ 502,793 Equity securities held for trading $ 3,235 $ 972 $ — $ 4,207 Loan level derivatives — 22,013 — 22,013 Risk participation-out agreements — 344 — 344 Foreign exchange contracts — 131 — 131 Liabilities: Loan level derivatives $ — $ 22,013 $ — $ 22,013 Risk participation-in agreements — 84 — 84 Foreign exchange contracts — 123 — 123 Investment Securities Available-for-Sale The fair value of investment securities is based principally on market prices and dealer quotes received from third-party and nationally-recognized pricing services for identical investment securities such as U.S. Treasury and agency securities. During the 3rd quarter of 2018, the Company re-designated all equity securities as held-for-trading and they are included in levels 1 and 2. These prices are validated by comparing the primary pricing source with an alternative pricing source when available. When quoted market prices for identical securities are unavailable, the Company uses market prices provided by independent pricing services based on recent trading activity and other observable information, including but not limited to market interest-rate curves, referenced credit spreads and estimated prepayment speeds where applicable. These investments include GSE debentures, GSE mortgage-related securities, SBA commercial loan asset backed securities, corporate debt securities, and trust preferred securities, all of which are included in Level 2. As of December 31, 2019 and December 31, 2018 , no investment securities were valued using pricing models included in Level 3. Additionally, management reviews changes in fair value from period to period and performs testing to ensure that prices received from the third parties are consistent with management's expectation of the market. Changes in the prices obtained from the pricing service are analyzed from month to month, taking into consideration changes in market conditions including changes in mortgage spreads, changes in U.S. Treasury security yields and changes in generic pricing of 15 -year and 30 -year securities. Additional analysis may include a review of prices provided by other independent parties, a yield analysis, a review of average life changes using Bloomberg analytics and a review of historical pricing for a particular security. Equity Securities Held-for-Trading The fair value of equity securities held-for-trading is based principally on market prices and dealer quotes received from third-party and nationally-recognized pricing services. The Company's equity securities are priced this way and are included in Level 1. These prices are validated by comparing the primary pricing source with an alternative pricing source when available. Loan Level Derivatives The fair values for the interest-rate swap assets and liabilities represent a Level 2 valuation and are based on settlement values adjusted for credit risks associated with the counterparties and the Company and observable market interest rate curves. Credit risk adjustments consider factors such as the likelihood of default by the Company and its counterparties, its net exposures and remaining contractual life. To date, the Company has not realized any losses due to a counterparty's inability to pay any net uncollateralized position. Refer also to Note 16, "Derivatives and Hedging Activities." There are no assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the year ended December 31, 2019 and December 31, 2018 . There were no transfers between levels for assets and liabilities recorded at fair value on a recurring basis during 2019 or 2018 . Assets and Liabilities Recorded at Fair Value on a Non-Recurring Basis Assets and liabilities measured at fair value on a non-recurring basis as of December 31, 2019 and 2018 are summarized below: Carrying Value as of December 31, 2019 Level 1 Level 2 Level 3 Total (In Thousands) Assets measured at fair value on a non-recurring basis: Collateral-dependent impaired loans and leases $ — $ — $ 2,243 $ 2,243 Repossessed assets — 2,631 — 2,631 Total assets measured at fair value on a non-recurring basis $ — $ 2,631 $ 2,243 $ 4,874 Carrying Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (In Thousands) Assets measured at fair value on a non-recurring basis: Collateral-dependent impaired loans and leases $ — $ — $ 11,451 $ 11,451 OREO — — 3,054 3,054 Repossessed assets — 965 — 965 Total assets measured at fair value on a non-recurring basis $ — $ 965 $ 14,505 $ 15,470 Collateral-Dependent Impaired Loans and Leases For nonperforming loans and leases where the credit quality of the borrower has deteriorated significantly, fair values of the underlying collateral were estimated using purchase and sales agreements (Level 2), or comparable sales or recent appraisals (Level 3), adjusted for selling costs and other expenses. Other Real Estate Owned The Company records OREO at the lower of cost or fair value. In estimating fair value, the Company utilizes purchase and sales agreements (Level 2) or comparable sales, recent appraisals or cash flows discounted at an interest rate commensurate with the risk associated with these cash flows (Level 3), adjusted for selling costs and other expenses. Repossessed Assets Repossessed assets are carried at estimated fair value less costs to sell based on auction pricing (Level 2). The table below presents quantitative information about significant unobservable inputs (Level 3) for assets measured at fair value on a recurring basis at the dates indicated. Fair Value Valuation Technique At December 31, 2019 At December 31, 2018 (Dollars in Thousands) Collateral-dependent impaired loans and leases $ 2,243 $ 11,451 Appraisal of collateral (1) Other real estate owned — 3,054 Appraisal of collateral (1) _______________________________________________________________________________ (1) Fair value is generally determined through independent appraisals of the underlying collateral. The Company may also use another available source of collateral assessment to determine a reasonable estimate of the fair value of the collateral. Appraisals may be adjusted by management for qualitative factors such as economic factors and estimated liquidation expenses. The range of the unobservable inputs used may vary but is generally 0% - 10% on the discount for costs to sell and 0% - 15% on appraisal adjustments. Summary of Estimated Fair Values of Financial Instruments The following table presents the carrying amount, estimated fair value, and placement in the fair value hierarchy of the Company's financial instruments at the dates indicated. This table excludes financial instruments for which the carrying amount approximates fair value. Financial assets for which the fair value approximates carrying value include cash and cash equivalents, restricted equity securities, and accrued interest receivable. Financial liabilities for which the fair value approximates carrying value include non-maturity deposits, short-term borrowings, and accrued interest payable. There were no transfers between levels during 2019 . Fair Value Measurements Carrying Value Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs (In Thousands) At December 31, 2019 Financial assets: Investment securities held-to-maturity: GSE debentures $ 31,228 $ 31,290 $ — $ 31,290 $ — GSE MBSs 9,360 9,279 — 9,279 — Municipal obligations 45,692 46,514 — 46,514 — Foreign government obligations 500 478 — — 478 Loans and leases, net 6,676,734 6,697,583 — — 6,697,583 Restricted equity securities 53,818 53,818 — — 53,818 Financial liabilities: Certificates of deposit 2,021,642 2,026,683 — 2,026,683 — Borrowed funds 902,749 902,670 — 902,670 — At December 31, 2018 Financial assets: Investment securities held-to-maturity: GSE debentures $ 50,546 $ 49,601 $ — $ 49,601 $ — GSE MBSs 11,426 11,131 — 11,131 — Municipal obligations 52,304 51,598 — 51,598 — Foreign government obligations 500 500 — — 500 Loans held-for-sale 3,247 3,247 — 3,247 — Loans and leases, net 6,244,824 6,154,704 — — 6,154,704 Restricted equity securities 61,751 61,751 — — 61,751 Financial liabilities: Certificates of deposit 1,789,165 1,778,860 — 1,778,860 — Borrowed funds 920,542 886,545 — 886,545 — Investment Securities Held-to-Maturity The fair values of certain investment securities held-to-maturity are estimated using market prices provided by independent pricing services based on recent trading activity and other observable information, including but not limited to market interest-rate curves, referenced credit spreads and estimated prepayment speeds where applicable. These investments include GSE debentures, GSE MBSs, and municipal obligations, all of which are included in Level 2. Additionally, fair values of foreign government obligations are based on comparisons to market prices of similar securities and are considered to be Level 3. Loans Held-for-Sale Fair value is measured using quoted market prices when available. These assets are typically categorized as Level 1. If quoted market prices are not available, comparable market values may be utilized. These assets are typically categorized as Level 2. Loans and Leases The fair values of performing loans and leases was estimated by segregating the portfolio into its primary loan and lease categories—commercial real estate mortgage, multi-family mortgage, construction, commercial, equipment financing, condominium association, residential mortgage, home equity and other consumer. These categories were further disaggregated based upon significant financial characteristics such as type of interest rate (fixed / variable) and payment status (current / past-due). The Company discounts the contractual cash flows for each loan category using interest rates currently being offered for loans with similar terms to borrowers of similar quality and incorporates estimates of future loan prepayments. Restricted Equity Securities The fair values of certain restricted equity securities are estimated using observable inputs adjusted for other unobservable information, including but not limited to probability assumptions and similar discounts where applicable. These restricted equity securities are considered to be Level 3. Deposits The fair values of deposit liabilities with no stated maturity (demand, NOW, savings and money market savings accounts) are equal to the carrying amounts payable on demand. The fair value of certificates of deposit represents contractual cash flows discounted using interest rates currently offered on deposits with similar characteristics and remaining maturities. The fair value estimates for deposits do not include the benefit that results from the low-cost funding provided by the Company's core deposit relationships (deposit-based intangibles). Borrowed Funds The fair value of federal funds purchased is equal to the amount borrowed. The fair value of FHLBB advances and repurchase agreements represents contractual repayments discounted using interest rates currently available for borrowings with similar characteristics and remaining maturities. The fair values reported for retail repurchase agreements are based on the discounted value of contractual cash flows. The discount rates used are representative of approximate rates currently offered on borrowings with similar characteristics and maturities. The fair values reported for subordinated deferrable interest debentures are based on the discounted value of contractual cash flows. The discount rates used are representative of approximate rates currently offered on instruments with similar terms and maturities.

Condensed Parent Company Financ

Condensed Parent Company Financial Statements	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Condensed Parent Company Financial Statements	Condensed Parent Company Financial Statements Condensed Parent Company Balance Sheets as of December 31, 2019 and 2018 and Statements of Income for the years ended December 31, 2019 , 2018 and 2017 are as follows. The Statement of Stockholders' Equity is not presented below as the parent company's stockholders' equity is that of the consolidated company. Balance Sheets At December 31, 2019 2018 (In Thousands) ASSETS Cash and due from banks $ 35,736 $ 33,663 Short-term investments 33 33 Total cash and cash equivalents 35,769 33,696 Equity securities held-for-trading 2,569 3,235 ESOP loan to Brookline Bank 752 1,002 Intercompany loan to Brookline Bank 30,000 40,000 Restricted equity securities 252 101 Premises and equipment, net 2,403 4,318 Deferred tax asset 1,742 1,499 Investment in subsidiaries, at equity 924,352 864,798 Goodwill 35,267 35,267 Other assets 12,116 5,400 Total assets $ 1,045,222 $ 989,316 LIABILITIES AND STOCKHOLDERS' EQUITY Borrowed funds $ 83,591 $ 83,433 Deferred tax liability — — Accrued expenses and other liabilities 16,025 5,743 Total liabilities 99,616 89,176 Stockholders' equity: Common stock, $0.01 par value; 200,000,000 shares authorized; 85,177,172 shares issued and 85,177,172 shares issued, respectively 852 852 Additional paid-in capital 736,601 755,629 Retained earnings, partially restricted 265,376 212,838 Accumulated other comprehensive loss 2,283 (9,460 ) Treasury stock, at cost; 5,003,127 shares and 5,020,025 shares, respectively (59,073 ) (59,120 ) Unallocated common stock held by ESOP; 79,548 shares and 109,950 shares, respectively (433 ) (599 ) Total stockholders' equity 945,606 900,140 Total liabilities and stockholders' equity $ 1,045,222 $ 989,316 Statements of Income Year Ended December 31, 2019 2018 2017 (In Thousands) Interest and dividend income: Dividend income from subsidiaries $ — $ — $ 7,317 Marketable and restricted equity securities 147 37 — ESOP loan to Brookline Bank 77 98 120 Intercompany loan to Brookline Bank 1,183 1,722 532 Total interest and dividend income 1,407 1,857 7,969 Interest expense: Borrowed funds 5,274 5,223 5,123 Net interest income (3,867 ) (3,366 ) 2,846 Non-interest income: Gain on securities, net 467 71 — Other — 16 — Total non-interest income 467 87 — Non-interest expense: Compensation and employee benefits (1) (507 ) 345 391 Occupancy 1,589 1,586 1,584 Equipment and data processing (1) (770 ) (798 ) (1,011 ) Directors' fees 461 417 453 Franchise taxes 306 321 180 Insurance 543 534 528 Professional services 548 364 470 Advertising and marketing 31 19 4 Merger and acquisition expense — 452 411 Other (1) (1,139 ) (1,140 ) (1,224 ) Total non-interest expense 1,062 2,100 1,786 Loss before income taxes (4,462 ) (5,379 ) 1,060 Credit for income taxes (969 ) (1,976 ) (1,944 ) Loss before equity in undistributed income of subsidiaries (3,493 ) (3,403 ) 3,004 Equity in undistributed income of subsidiaries 91,210 86,465 47,514 Net income $ 87,717 $ 83,062 $ 50,518 _______________________________________________________________________________ (1) The Parent Company received a net benefit in 2019, 2018 and 2017 from the intercompany allocation of expense that is eliminated in consolidation. Statements of Cash Flows Year Ended December 31, 2019 2018 2017 (In Thousands) Cash flows from operating activities: Net income attributable to parent company $ 87,717 $ 83,062 $ 50,518 Adjustments to reconcile net income to net cash provided from operating activities: Equity in undistributed income of subsidiaries (91,210 ) (86,465 ) (47,514 ) Depreciation of premises and equipment 2,824 3,073 2,856 Amortization of debt issuance costs 100 100 100 Equity securities held-for-trading 666 (3,235 ) — Other operating activities, net 47,296 (31,014 ) (5,885 ) Net cash provided from (used for) operating activities 47,393 (34,479 ) 75 Cash flows from investing activities: Repayment of ESOP loan by Brookline Bank 250 250 250 Pay down (issuance) of intercompany loan to Brookline Bank 10,000 40,000 (80,000 ) Purchase of restricted equity securities (151 ) (1 ) — Purchase of premises and equipment (909 ) (1,359 ) (1,942 ) Net cash provided from (used for) investing activities 9,190 38,890 (81,692 ) Cash flows from financing activities: Proceeds from issuance of common stock — — 81,943 Common stock issued for acquisition — 55,183 — Redemption of noncontrolling interest in subsidiary (18,470 ) — — Payment of dividends to owners of noncontrolling interest in subsidiary (930 ) — — Payment of dividends on common stock (35,110 ) (31,441 ) (27,035 ) Net cash (used for) provided from financing activities (54,510 ) 23,742 54,908 Net increase (decrease) in cash and cash equivalents 2,073 28,153 (26,709 ) Cash and cash equivalents at beginning of year 33,696 5,543 32,252 Cash and cash equivalents at end of year $ 35,769 $ 33,696 $ 5,543 Supplemental disclosures of cash flow information: Acquisition of First Commons Bank, N.A.: Fair value of assets acquired, net of cash and cash equivalents acquired $ — $ 292,025 $ — Fair value of liabilities assumed — 278,988 —

Quarterly Results of Operations

Quarterly Results of Operations (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations (Unaudited)	Quarterly Results of Operations (Unaudited) 2019 Quarters Fourth Third Second First (Dollars in Thousands Except Per Share Data) Interest and dividend income $ 87,450 $ 87,906 $ 87,184 $ 85,086 Interest expense 23,519 24,670 24,050 22,087 Net interest income 63,931 63,236 63,134 62,999 Provision for credit losses 3,602 871 3,757 1,353 Net interest income after provision for credit losses 60,329 62,365 59,377 61,646 Loan level derivative income, net 2,494 2,251 1,772 1,745 (Loss) gain on investment securities, net 133 (116 ) 357 134 Gain on sales of loans and leases held-for-sale 309 550 561 289 Other non-interest income 4,820 5,244 4,788 4,462 Amortization of identified intangible assets (420 ) (421 ) (420 ) (402 ) Other non-interest expense (38,395 ) (39,770 ) (39,184 ) (38,469 ) Income before provision for income taxes 29,270 30,103 27,251 29,405 Provision for income taxes 7,087 7,507 6,780 6,895 Net income before noncontrolling interest in subsidiary 22,183 22,596 20,471 22,510 Less net income attributable to noncontrolling interest in subsidiary — — — 43 Net income attributable to Brookline Bancorp, Inc. $ 22,183 $ 22,596 $ 20,471 $ 22,467 Earnings per share: Basic $ 0.28 $ 0.28 $ 0.26 $ 0.28 Diluted 0.28 0.28 0.26 0.28 Average common shares outstanding: Basic 79,682,724 79,700,403 79,669,922 79,658,583 Diluted 79,845,447 79,883,510 79,886,292 79,843,578 Common stock price: High $ 16.83 $ 15.39 $ 15.92 $ 16.23 Low 14.36 13.73 14.35 13.90 Dividends per share $ 0.115 $ 0.110 $ 0.110 $ 0.105 2018 Quarters Fourth Third Second First (Dollars in Thousands Except Per Share Data) Interest and dividend income $ 83,544 $ 80,636 $ 78,074 $ 71,639 Interest expense 20,385 18,304 15,357 12,148 Net interest income 63,159 62,332 62,717 59,491 Provision for credit losses 123 2,717 1,470 641 Net interest income after provision for credit losses 63,036 59,615 61,247 58,850 Loan level derivative income, net 1,811 2,192 571 866 Gain on sales of investment securities, net (692 ) (243 ) — 1,162 Gain on sales of loans and leases held-for-sale 327 535 722 299 Other non-interest income 5,015 4,585 4,233 3,841 Amortization of identified intangible assets (537 ) (537 ) (539 ) (467 ) Other non-interest expense (39,745 ) (36,773 ) (37,163 ) (39,471 ) Income before provision for income taxes 29,215 29,374 29,071 25,080 Provision for income taxes 7,055 6,140 7,342 5,652 Net income before noncontrolling interest in subsidiary 22,160 23,234 21,729 19,428 Less net income attributable to noncontrolling interest in subsidiary 1,022 774 898 795 Net income attributable to Brookline Bancorp, Inc. $ 21,138 $ 22,460 $ 20,831 $ 18,633 Earnings per share: Basic $ 0.26 $ 0.28 $ 0.26 $ 0.24 Diluted 0.26 0.28 0.26 0.24 Average common shares outstanding: Basic 80,258,489 80,315,050 80,184,977 77,879,593 Diluted 80,407,558 80,515,467 80,505,614 78,167,800 Common stock price: High $ 16.97 $ 19.05 $ 19.25 $ 17.05 Low 12.86 16.70 15.90 15.60 Dividends per share $ 0.105 $ 0.100 $ 0.100 $ 0.090

Revenue from Contracts with Cus

Revenue from Contracts with Customers (Notes)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	Revenue from Contracts with Customers Overview Revenue from contracts with customers in the scope of Accounting Standards Codification (“ASC”) ("Topic 606") is measured based on the consideration specified in the contract with a customer and excludes amounts collected on behalf of third parties. The Company recognizes revenue from contracts with customers when it satisfies its performance obligations. The Company’s performance obligations are generally satisfied as services are rendered and can either be satisfied at a point in time or over time. Unsatisfied performance obligations at the report date are not material to our consolidated financial statements. In certain cases, other parties are involved with providing services to our customers. If the Company is a principal in the transaction (providing services itself or through a third party on its behalf), revenues are reported based on the gross consideration received from the customer and any related expenses are reported gross in noninterest expense. If the Company is an agent in the transaction (referring to another party to provide services), the Company reports its net fee or commission retained as revenue. Accounting Policy Updates The Company adopted Topic 606, “Revenue from Contracts with Customers” effective January 1, 2018 and has applied the guidance to all contracts within the scope of Topic 606 as of that date. As a result, the Company has modified its accounting policy for revenue recognition as detailed in this Note. As discussed in Note 1, the Company applied Topic 606 using the modified retrospective method, therefore, the prior period comparative information has not been adjusted and continues to be reported under Topic 605. There was no cumulative effect adjustment as of January 1, 2018, and there were no material changes to our consolidated financial statements at or for the twelve months ended December 31, 2019 , as a result of adopting Topic 606. The Company applied the practical expedient pertaining to contracts with original expected duration of one year or less and does not disclose information about remaining performance obligations on such contracts. The Company also applied the practical expedient pertaining to contracts for which, at contract inception, the period between when the entity transfers the services and when the customer pays for those services will be one year or less. As such, the Company does not adjust the consideration from customers for the effects of a significant financing component. A substantial portion of the Company’s revenue is specifically excluded from the scope of Topic 606. This exclusion is associated with financial instruments, including interest income on loans and investment securities, in addition to loan derivative income and gains on loan and investment sales. For the revenue that is in-scope of Topic 606, the following is a description of principal activities from which the Company generates its revenue from contracts with customers, separated by the timing of revenue recognition. Revenue Recognized at a Point in Time The Company recognizes revenue that is transactional in nature and such revenue is earned at a point in time. Revenue that is recognized at a point in time includes card interchange fees (fee income related to debit card transactions), ATM fees, wire transfer fees, overdraft charge fees, and stop-payment and returned check fees. Additionally, revenue is collected from loan fees, such as letters of credit, line renewal fees and application fees. Such revenue is derived from transactional information and is recognized as revenue immediately as the transactions occur or upon providing the service to complete the customer’s transaction. Revenue Recognized Over Time The Company recognizes revenue over a period of time, generally monthly, as services are performed and performance obligations are satisfied. Such revenue includes commissions on investments, insurance sales and service charges on deposit accounts. Fee revenue from service charges on deposit accounts represent the service charges assessed to customers who hold deposit accounts at the Bank.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events First Ipswich Bank On February 15, 2020, Brookline Bank completed the merger of First Ipswich Bank and its subsidiaries with and into Brookline Bank. First Ipswich was already a wholly-owned subsidiary of the Company, therefore there was no tax impact and minimal impact to customers. All of First Ipswich Bank's six branch locations were retained and converted to Brookline Bank branches. The Company has evaluated subsequent events other than the matters described above and through the date of issuance.

Basis of Presentation (Policies

Basis of Presentation (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies
Basis of Accounting	The Company's consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles ("GAAP") as set forth by the Financial Accounting Standards Board ("FASB") in its Accounting Standards Codification and through the rules and interpretive releases of the Securities and Exchange Commission ("SEC") under the authority of federal securities laws.
Consolidation	The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances are eliminated in consolidation.
Use of Estimates	In preparing these consolidated financial statements, management is required to make significant estimates and assumptions that affect the reported amounts of assets, liabilities, income, expenses and disclosure of contingent assets and liabilities. Actual results could differ from those estimates based upon changing conditions, including economic conditions and future events. Material estimates that are particularly susceptible to significant changes in the near-term include the determination of the allowance for loan and lease losses, the determination of fair market values of assets and liabilities, including acquired loans, the review of goodwill and intangibles for impairment and the review of deferred tax assets for valuation allowance. The judgments used by management in applying these significant estimates may be affected by a further and prolonged deterioration in the economic environment, which may result in changes to future financial results. For example, subsequent evaluations of the loan and lease portfolio, in light of the factors then prevailing, may result in significant changes in the allowance for loan and lease losses in future periods, and the inability to collect outstanding principal may result in increased loan and lease losses.
Reclassification	Reclassification
Cash and Cash Equivalents	Cash and Cash Equivalents For purposes of reporting asset balances and cash flows, cash and cash equivalents includes cash on hand and due from banks (including cash items in process of clearing), interest-bearing deposits with banks, federal funds sold, money market mutual funds and other short-term investments with original maturities of three months or less.
Investment Securities	Investment Securities Investment securities, other than those reported as short-term investments, are classified at the time of purchase as "available-for-sale," "held-to-maturity," or "held-for-trading." Classification is periodically re-evaluated for consistency with the Company's goals and objectives. Equity investments in the Federal Home Loan Bank of Boston ("FHLBB"), the Federal Reserve Bank of Boston and other restricted equities are discussed in more detail in Note 5, "Restricted Equity Securities." Investment Securities Available-for-Sale, Held-to-Maturity, and Held-for-Trading Investment securities for which the Company has the positive intent and ability to hold to maturity are classified as held-to-maturity and carried at amortized cost. Those investment securities held for indefinite periods of time but not necessarily to maturity are classified as available-for-sale. Investment securities held for indefinite periods of time include investment securities that management intends to use as part of its asset/liability, liquidity, and/or capital management strategies and may be sold in response to changes in interest rates, maturities, asset/liability mix, liquidity needs, regulatory capital needs or other business factors. Investment securities available-for-sale are carried at estimated fair value, primarily obtained from a third-party pricing service, with unrealized gains and losses reported on an after-tax basis in stockholders' equity as accumulated other comprehensive income or loss. Investment securities expected to be held for very short term duration, used for hedging, or are marketable equity securities are typically designated held-for-trading. Held-for-trading securities are carried at estimated fair value principally based on market prices and dealer quotes received from third-party and nationally-recognized pricing services. Gains and losses for held-for-trading are reported on the income statement as gains on investment securities, net. As of December 31, 2019 and 2018 , the Company did not make any adjustments to the prices provided by the third-party pricing service. Security transactions are recorded on the trade date. Realized gains and losses are determined using the specific identification method and are recorded in non-interest income. Interest and dividends on securities are recorded using the accrual method. Premiums and discounts on securities are amortized or accreted into interest income using the level-yield method over the remaining period to contractual maturity, adjusted for the effect of actual prepayments in the case of mortgage-backed securities ("MBSs") and collateralized mortgage obligations ("CMOs"). These estimates of prepayment assumptions are made based upon the actual performance of the underlying security, current interest rates, the general market consensus regarding changes in mortgage interest rates, the contractual repayment terms of the underlying loans, the priority rights of the investors to the cash flows from the mortgage securities and other economic conditions. When differences arise between anticipated prepayments and actual prepayments, the effective yield is recalculated to reflect actual payments to date and anticipated future payments. Unamortized premium or discount is adjusted to the amount that would have existed had the new effective yield been applied since purchase, with a corresponding charge or credit to interest income. Management evaluates securities for other-than-temporary impairment ("OTTI") on a periodic basis. Factors considered in determining whether an impairment is OTTI include: (1) the length of time and the extent to which the fair value has been less than amortized cost, (2) projected future cash flows, (3) the financial condition and near-term prospects of the issuers, and (4) the intent and ability of the Company to hold the investment for a period of time sufficient to allow for any anticipated recovery in fair value. The Company records an OTTI loss in an amount equal to the entire difference between the fair value and amortized cost if: (1) the Company intends to sell an impaired investment security, (2) it is more likely than not that the Company will be required to sell the investment security before its amortized cost, or (3) for debt securities, the present value of expected future cash flows is not sufficient to recover the entire amortized cost basis. If an investment security is determined to be OTTI but the Company does not intend to sell the investment security, only the credit portion of the estimated loss is recognized in earnings, with the non credit portion of the loss recognized in other comprehensive income. Restricted Equity Securities
Loans	Loans Originated Loans Loans the Company originates for the portfolio, and for which it has the intent and ability to hold to maturity, are reported at amortized cost, inclusive of deferred loan origination fees and expenses, less unadvanced funds due borrowers on loans and the allowance for loan and lease losses. Interest income on loans and leases originated for the portfolio is accrued on unpaid principal balances as earned. Loan origination fees and direct loan origination costs are deferred, and the net fee or cost is recognized in interest income using the interest method. Deferred amounts are recognized for fixed-rate loans over the contractual life of the loans and for adjustable-rate loans over the period of time required to adjust the contractual interest rate to a yield approximating a market rate at the origination date. If a loan is prepaid, the unamortized portion of the loan origination costs, including third party referral related costs not subject to rebate from the dealer, is charged to income. Loans and Leases Held-for-Sale Management identifies and designates certain newly originated loans and leases for sale to specific financial institutions, subject to the underwriting criteria of those financial institutions. These loans and leases are held for sale and are carried at the lower of cost or market as determined in the aggregate. Deferred loan fees and costs are included in the determination of the gain or loss on sale. Acquired Loans Acquired loans that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments receivable are initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance. The difference between the undiscounted cash flows expected at acquisition and the recorded fair value of the loan, or the “accretable yield,” is recognized as interest income on a level-yield method over the life of the loan. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “nonaccretable difference,” are not recognized as a yield adjustment or as a loss accrual or a valuation allowance. The Company uses a model to reforecast expected cash flows on these acquired loans. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows are recognized as impairment. Valuation allowances on these impaired loans reflect only losses incurred after the acquisition (meaning the present value of all cash flows expected at acquisition that ultimately are not to be received). For the First Commons Bank portfolio, minimal loss is expected from the loan portfolio based on historical performance, management’s due diligence, and market conditions. Therefore, the fair value of the loan portfolio was calculated on an individual loan basis using a discounted cash flow analysis factoring in the contractual terms of the loans, current market pricing, and prepayment expectations.
Non-Performing Loans	Nonperforming Loans Nonaccrual Loans Accrual of interest on loans generally is discontinued when contractual payment of principal or interest becomes past due 90 days or, if in management's judgment, reasonable doubt exists as to the full timely collection of interest. Exceptions may be made if the loan has matured and is in the process of renewal or is well-secured and in the process of collection. When a loan is placed on nonaccrual status, interest accruals cease and uncollected accrued interest is reversed and charged against current interest income. Interest payments on nonaccrual loans are generally applied to principal. If collection of the principal is reasonably assured, interest payments are recognized as income on the cash basis. Loans are generally returned to accrual status when principal and interest payments are current, full collectability of principal and interest is reasonably assured and a consistent record of at least six consecutive months of performance has been achieved. Impaired Loans A loan is considered to be impaired when, based on current information and events, it is probable that the Company will be unable to collect all amounts due (both interest and principal) according to the contractual terms of the loan agreement. Smaller-balance, homogeneous loans that are evaluated collectively for impairment, such as residential, home equity and other consumer loans are specifically excluded from the impaired loan portfolio except where the loan is classified as a troubled debt restructuring. The Company has defined the population of impaired loans to include nonaccrual loans and troubled debt restructured ("TDR") loans. When the ultimate collectability of the total principal of an impaired loan or lease is in doubt and the loan is on nonaccrual status, all payments are applied to principal, under the cost recovery method. When the ultimate collectability of the total principal of an impaired loan or lease is not in doubt and the loan or lease is on nonaccrual status, contractual interest is credited to interest income when received, under the cash basis method. The value of an impaired loan is measured based upon the present value of expected future cash flows discounted at the loan's effective interest rate, or the fair value of the collateral if the loan is collateral-dependent and its payment is expected solely based on the underlying collateral. For impaired loans deemed collateral dependent, where impairment is measured using the fair value of the collateral, the Company will either obtain a new appraisal or use another available source of collateral assessment to determine a reasonable estimate of the fair value of the collateral. Interest collected on impaired loans is either applied against principal or reported as income according to management's judgment as to the collectability of principal. If management does not consider a loan ultimately collectible within an acceptable time frame, payments are applied as principal to reduce the loan balance. If full collection of the remaining recorded investment should subsequently occur, interest receipts are recorded as interest income on a cash basis. Troubled Debt Restructured Loans In cases where a borrower experiences financial difficulties and the Company makes certain concessionary modifications to contractual terms, the loan is classified as a TDR loan. In determining whether a debtor is experiencing financial difficulties, the Company considers, among other factors, whether the debtor is in payment default or is likely to be in payment default in the foreseeable future without the modification, if the debtor declared or is in the process of declaring bankruptcy, there is substantial doubt that the debtor will continue as a going concern, the debtor's entity-specific projected cash flows will not be sufficient to service its debt, or the debtor cannot obtain funds from sources other than the existing creditors at market terms for debt with similar risk characteristics. Large groups of small-balance homogeneous loans such as residential real estate, residential construction, home equity and other consumer portfolios are collectively evaluated for impairment. As such, the Company does not typically identify individual loans within these groupings as impaired loans or for impairment evaluation and disclosure. However, the Company evaluates all TDRs for impairment on an individual loan basis regardless of loan type. Modifications may include interest-rate reductions, short-term (defined as one year or less) changes in payment structure to interest-only payments, short-term extensions of the loan's original contractual term, or less frequently, principal forgiveness, interest capitalization, forbearance and other actions intended to minimize economic loss and avoid foreclosure or repossession of collateral. Typically, TDRs are placed on nonaccrual status and reported as nonperforming loans. Generally, a nonaccrual loan that is restructured remains on nonaccrual for a period of six months to demonstrate that the borrower can meet the restructured terms; however, performance prior to the restructuring, or significant events that coincide with the restructuring, are considered in assessing whether the borrower can meet the new terms and may result in the loan being returned to accrual status at the time of restructuring or after a shorter performance period. If the borrower's ability to meet the revised payment schedule is not reasonably assured, the loan remains classified as a nonaccrual loan. Loans restructured at an interest rate equal to or greater than that of a new loan with comparable risk at the time the loan agreement is modified may be excluded from restructured loan disclosures in years subsequent to the restructuring if they are in compliance with the modified terms.
Allowance for Loan and Lease Losses	Allowance for Loan and Lease Losses Management has established a methodology to determine the adequacy of the allowance for loan and lease losses that assesses the risks and losses inherent in the loan and lease portfolio. Additions to the allowance for loan and lease losses are made by charges to the provision for credit losses. Losses on loans and leases are charged off against the allowance when all or a portion of a loan or lease is considered uncollectible. Subsequent recoveries on loans previously charged off, if any, are credited to the allowance when realized. Management uses a consistent and systematic process and methodology to evaluate the adequacy of the allowance for loan and lease losses on a quarterly basis. For purposes of determining the allowance for loan and lease losses, the Company has segmented certain loans and leases in the portfolio by product type into the following segments: (1) commercial real estate loans, (2) commercial loans and leases, (3) and consumer loans. Portfolio segments are further disaggregated into classes based on the associated risks within the segments. Commercial real estate loans are divided into three classes: commercial real estate mortgage loans, multi-family mortgage loans, and construction loans. Commercial loans and leases are divided into three classes: commercial loans which includes taxi medallion loans, equipment financing, and loans to condominium associations. Consumer loans are divided into three classes: residential mortgage loans, home equity loans, and other consumer loans. A formula-based credit evaluation approach is applied to each group, coupled with an analysis of certain loans for impairment. The general allowance related to loans collectively evaluated for impairment is determined using a formula-based approach utilizing the risk ratings of individual credits and loss factors derived from historic portfolio loss rates over a lookback period, which include estimates of incurred losses over an estimated loss emergence period (“LEP”). The LEP was generated utilizing a charge-off look-back analysis which studied the time from the first indication of elevated risk of repayment (or other early event indicating a problem) to eventual charge-off to support the LEP considered in the allowance calculation. This reserving methodology established the approximate number of months of LEP that represents incurred losses for each portfolio. In addition to quantitative measures, relevant qualitative factors include, but are not limited to: (1) levels and trends in past due and impaired loans, (2) levels and trends in charge-offs, (3) changes in underwriting standards, policy exceptions, and credit policy, (4) experience of lending management and staff, (5) economic trends, (6) industry conditions, (7) effects of changes in credit concentrations, (8) interest rate environment, and (9) regulatory and other changes. The general allowance related to the acquired loans collectively evaluated for impairment is determined based upon the degree, if any, of deterioration in the pooled loans subsequent to acquisition. The qualitative factors used in the determination are the same as those used for originated loans. During 2015, the Company enhanced and refined its general allowance methodology. Under the enhanced methodology, management combined the historical loss histories of the Banks to generate a single set of historical loss ratios. Management believes it is appropriate to aggregate the ratios as the Banks share common environmental factors, operate in similar geographic markets, and utilize common underwriting standards in accordance with the Company's Credit Policy. In prior periods, a historical loss history applicable to each Bank was used. Management employed a similar analysis for the consolidation of the qualitative factors as it did for the quantitative factors. Again, management believes the realignment of the existing nine qualitative factors used at each of the Banks into a single group of factors used for the Company is appropriate based on the commonality of environmental factors, markets and underwriting standards among the Banks. Prior to 2015, each of the Banks utilized a set of qualitative factors applicable to each Bank. The Company’s December 31, 2019 allowance calculation included a further segmentation of the commercial loans and leases to reflect the increased risk in the Company’s taxi medallion portfolio. As of December 31, 2019 , this portfolio is approximately $10.3 million . Based on industry conditions, management established a loss factor for this portfolio that best represents the changing risks associated with it. Based on the refinements to the Company’s allowance methodology discussed above, management determined that the potential risks anticipated by the unallocated allowance are now incorporated into the allowance methodology, making the unallocated allowance unnecessary. Prior to 2015, the unallocated allowance was used to recognize the estimated risk associated with the allocated general and specific allowances. It incorporated management’s evaluation of existing conditions that were not included in the allocated allowance determinations and provided for losses that arise outside of the ordinary course of business. Specific valuation allowances are established for impaired originated loans with book values greater than the discounted present value of expected future cash flows or, in the case of collateral-dependent impaired loans, for any excess of a loan's book balance and the fair value of its underlying collateral. Specific valuation allowances are established for acquired loans with deterioration in the discounted present value of expected future cash flows since acquisitions or, in the case of collateral dependent impaired loans, for any increase in the excess of a loan's book balance greater than the fair value of its underlying collateral. A specific valuation allowance for losses on TDR loans is determined by comparing the net carrying amount of the troubled debt restructured loan with the restructured loan's cash flows discounted at the original effective rate. Impaired loans are reviewed quarterly with adjustments made to the calculated reserve as necessary. As of December 31, 2019 , management believes that the methodology for calculating the allowance is sound and that the allowance provides a reasonable basis for determining and reporting on probable losses in the Company’s loan portfolios. Liability for Unfunded Commitments In the ordinary course of business, the Company enters into commitments to extend credit, commercial letters of credit, and standby letters of credit. Such financial instruments are recorded in the financial statements when they become payable. The credit risk associated with these commitments is evaluated in a manner similar to the allowance for loan losses.
Premises and Equipment	Premises and Equipment Premises and equipment are carried at cost less accumulated depreciation and amortization, except for land which is carried at cost. Premises and equipment are depreciated using the straight-line method over the estimated useful life of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful life of the improvements. Costs related to internal-use software development projects that provide significant new functionality are capitalized. Internal-use software is software acquired or modified solely to meet the Company's needs and for which there is no plan to market the software externally. Direct and indirect costs associated with the application development stage of internal use software are capitalized until such time that the software is substantially complete and ready for its intended use. Capitalized costs are amortized on a straight-line basis over the remaining estimated life of the software. Computer software and development costs incurred in the preliminary project stage, as well as training and maintenance costs, are expensed as incurred.
Leases	Leases
Bank-Owned Life Insurance	Bank-Owned Life Insurance The Company acquired bank-owned life insurance ("BOLI") plans as part of its acquisitions of First Ipswich and BankRI. BOLI represents life insurance on the lives of certain current and former employees who have provided positive consent allowing their employer to be the beneficiary of such policies. BankRI and Brookline Bank are the beneficiaries of their respective policies. BankRI and Brookline Bank utilize BOLI as tax-efficient financing for their benefit obligations to their employees, including their retirement obligations and Supplemental Executive Retirement Plans ("SERPs"). Since BankRI and Brookline Bank are the primary beneficiaries of their respective insurance policies, increases in the cash value of the policies, as well as insurance proceeds received, are recorded in non-interest income and are not subject to income taxes. BOLI is recorded at the cash value of the policies, less any applicable cash surrender charges, and is reflected as an asset in the accompanying consolidated balance sheets. Cash proceeds, if any, are classified as cash flows from investing activities. The Company reviews the financial strength of the insurance carriers prior to the purchase of BOLI to ensure minimum credit ratings of at least investment grade. The financial strength of the carriers is reviewed at least annually, and BOLI with any individual carrier is limited to 10% of the Company's capital. Total BOLI is limited to 25%
Goodwill and Other Identified Intangible Assets	Goodwill and Other Identified Intangible Assets Goodwill represents the excess of the cost of an acquisition over the fair value of the net assets acquired. Goodwill and indefinite-lived identified intangible assets are not subject to amortization. Definite-lived identified intangible assets are assets resulting from acquisitions that are being amortized over their estimated useful lives. The recoverability of goodwill and identified intangible assets is evaluated for impairment at least annually. As part of this evaluation, the Company makes a qualitative assessment of whether it is more likely than not that the fair value of an acquired asset is greater than its carrying amount. If the Company qualitatively concludes that it is more likely than not that the fair value of an acquired asset is greater than its carrying amount, no further testing is necessary. If, however, the Company qualitatively concludes that the fair value of an acquired asset is less than its carrying value, the Company should recognize an impairment charge for the amount by which the carrying amount exceeds the fair value. The Company did not have any impairment of Goodwill and other identified intangible assets as of December 31, 2019 and 2018 .
OREO and Other Repossessed Assets	OREO and Other Repossessed Assets
Derivatives	Derivatives The Company utilizes loan level derivatives which consists of interest rate contracts (swaps, caps and floors), and risk participation agreements as part of the Company's interest-rate risk management strategy for certain assets and liabilities and not for speculative purposes. Based on the Company's intended use for the loan level derivatives at inception, the Company designates the derivative as either an economic hedge of an asset or liability, or a hedging instrument subject to the hedge accounting provisions of FASB ASC Topic 815, "Derivatives and Hedging." Loan level derivatives and foreign exchange contracts entered into on behalf of our customers are designated as economic hedges and are recorded at fair value within other assets or liabilities. Changes in the fair value of these non hedging derivatives are recorded directly through earnings at each reporting period.
Transfer of Financial Assets	Transfer of Financial Assets Transfers of financial assets are accounted for as sales when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (1) the assets have been isolated from the Company, (2) the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets, and (3) the Company does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity.
Securities Sold under Agreements to Repurchase	Securities Sold under Agreements to Repurchase The Company enters into sales of securities under agreements to repurchase with the Banks' commercial customers. These agreements are treated as financings, and the obligations to repurchase securities sold are reflected as a liability in the consolidated balance sheets. Securities pledged as collateral under agreements to repurchase are reflected as assets in the accompanying consolidated balance sheets.
Employee Benefits	Employee Benefits Costs related to the Company's 401(k) plan are recognized in current earnings. Costs related to the Company's nonqualified deferred compensation plan, SERPs and postretirement benefits are recognized over the vesting period or the related service periods of the participating employees. Changes in the funded status of postretirement benefits are recognized through comprehensive income in the year in which changes occur. Compensation expense for the Company's Employee Stock Ownership Program ("ESOP") is recorded at an amount equal to the shares allocated by the ESOP multiplied by the average fair market value of the shares during the year. The Company recognizes compensation expense ratably over the year based upon the Company's estimate of the number of shares expected to be allocated by the ESOP. The difference between the average fair market value and the cost of the shares allocated by the ESOP is recorded as an adjustment to additional paid-in capital. The fair value of restricted stock awards and stock option grants are determined as of the grant date and are recorded as compensation expense over the period in which the shares of restricted stock awards and stock options vest. Forfeitures are accounted for as they occur.
Fair Value Measurements	Fair Value Measurements ASC 820-10, "Fair Value Measurements and Disclosures," defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. A fair value measurement assumes that the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability. The price in the principal (or most advantageous) market used to measure the fair value of the asset or liability is not adjusted for transaction costs. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets and liabilities. It is not a forced transaction. Market participants are buyers and sellers in the principal market that are independent, knowledgeable, able to transact, and willing to transact. A fair-value hierarchy for valuation inputs that gives the highest priority to quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs are included in ASC 820. The fair value hierarchy is as follows: Level 1: Inputs are unadjusted quoted prices in active markets for assets and liabilities identical to those reported at fair value. Level 2: Inputs other than quoted prices included within Level 1. Level 2 inputs are observable either directly or indirectly. These inputs might include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, volatilities, prepayment speeds, credit risks, etc.) or inputs that are derived principally from or corroborated by market data by correlation or other means. Level 3: Inputs are unobservable inputs for an asset or liability that reflect an entity's own assumptions about the assumptions that market participants would use in pricing the assets or liabilities. These inputs are used to determine fair value only when observable inputs are not available.
Earnings per Common Share	Earnings per Common Share Basic earnings per share ("EPS") is computed by dividing net income by the weighted average number of shares of common stock outstanding for the applicable period, exclusive of Treasury shares, unearned ESOP shares and unvested shares of restricted stock. Diluted EPS is calculated after adjusting the denominator of the basic EPS calculation for the effect of all potential dilutive common shares outstanding during the period. The dilutive effects of options and unvested restricted stock
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Tax positions that are more likely than not to be sustained upon a tax examination are recognized in the Company's financial statements to the extent that the benefit is greater than 50% likely of being recognized. Interest resulting from underpayment of income taxes is classified as income tax expense in the first period the interest would begin accruing according to the provision of the relevant tax law. Penalties resulting from underpayment of income taxes are classified as income tax expense in the period for which the Company claims or expects to claim an uncertain tax position or in the period in which the Company's judgment changes regarding an uncertain tax position.
Treasury Stock	Treasury Stock Any shares repurchased under the Company's share repurchase programs were purchased in open-market transactions and are held as treasury stock. Treasury stock also consists of common stock withheld to satisfy federal, state and local income tax withholding requirements for employee restricted stock awards upon vesting. All treasury stock is held at cost.
Segment Reporting	Segment Reporting An operating segment is defined as a component of a business for which separate financial information is available that is evaluated regularly by the chief operating decision-maker in deciding how to allocate resources and evaluate performance. The Company is a bank holding company with subsidiaries engaged in the business of banking and activities closely related to banking. The Company's banking business provided substantially all of its total revenues and pre-tax income in 2019 , 2018 and 2017 . Therefore, the Company has determined to be a single segment.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, FASB issued ASU 2016-02, Leases (“ASU 2016-02”). This ASU requires lessees to record most leases on their balance sheet but recognize expenses on their income statements in a manner similar to current accounting. Subsequently, the FASB issued ASU 2018-10, ASU 2018-11, ASU 2018-20 and ASU 2019-01 to update provisions to ASU 2016-02. The Company has adopted all of the above mentioned ASU's regarding leases as of January 1, 2019. The standard had an impact on our consolidated balance sheet by recognizing right-of-use asset operating leases and operating lease liabilities on the balance sheet. However, there was no impact on our consolidated income statement as the timing of the expense recognition has not changed. Additional details can be found in Note 12.

Cash and Short-Term Investments

Cash and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Short-term investments	Short-term investments are summarized as follows: At December 31, 2019 2018 (In Thousands) FRB interest bearing reserve $ 39,964 $ 34,914 FHLB overnight deposits 4,237 4,628 Federal funds sold — 2,500 Total short-term investments $ 44,201 $ 42,042

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of securities available-for-sale securities	The following tables set forth investment securities available-for-sale, held-to-maturity and equity securities held-for-trading at the dates indicated: At December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In Thousands) Investment securities available-for-sale: GSE debentures $ 182,922 $ 2,939 $ 58 $ 185,803 GSE CMOs 87,001 22 1,091 85,932 GSE MBSs 153,049 797 503 153,343 SBA commercial loan asset-backed securities 34 — — 34 Corporate debt obligations 28,484 502 — 28,986 U.S. treasury bonds 44,675 338 116 44,897 Total investment securities available-for-sale $ 496,165 $ 4,598 $ 1,768 $ 498,995 Investment securities held-to-maturity: GSE debentures $ 31,228 $ 113 $ 51 $ 31,290 GSEs MBSs 9,360 — 81 9,279 Municipal obligations 45,692 822 — 46,514 Foreign government obligations 500 — 22 478 Total investment securities held-to-maturity $ 86,780 $ 935 $ 154 $ 87,561 Equity securities held-for-trading $ 561 $ 3,581 At December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In Thousands) Investment securities available-for-sale: GSE debentures $ 184,072 $ 99 $ 3,092 $ 181,079 GSE CMOs 107,363 17 4,250 103,130 GSE MBSs 169,334 124 4,369 165,089 SBA commercial loan asset-backed securities 51 — — 51 Corporate debt obligations 40,618 — 910 39,708 U.S. treasury bonds 13,812 65 141 13,736 Total investment securities available-for-sale $ 515,250 $ 305 $ 12,762 $ 502,793 Investment securities held-to-maturity: GSE debentures $ 50,546 $ 22 $ 967 $ 49,601 GSEs MBSs 11,426 — 295 11,131 Municipal obligations 52,304 10 716 51,598 Foreign government obligations 500 — — 500 Total investment securities held-to-maturity $ 114,776 $ 32 $ 1,978 $ 112,830 Equity securities held for trading 1,170 $ 4,207
Investment securities in a continuous unrealized loss position	Investment securities as of December 31, 2019 and 2018 that have been in a continuous unrealized loss position for less than twelve months or twelve months or longer are as follows: At December 31, 2019 Less than Twelve Months Twelve Months or Longer Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (In Thousands) Investment securities available-for-sale: GSE debentures $ 10,965 $ 58 $ — $ — $ 10,965 $ 58 GSE CMOs 28,659 217 55,885 874 84,544 1,091 GSE MBSs 42,046 115 42,257 388 84,303 503 SBA commercial loan asset-backed securities — — 33 — 33 — U.S. Treasury bonds 25,754 116 — — 25,754 116 Temporarily impaired investment securities available-for-sale 107,424 506 98,175 1,262 205,599 1,768 Investment securities held-to-maturity: GSE debentures 8,714 30 2,977 21 11,691 51 GSEs MBSs — — 9,257 81 9,257 81 Municipal obligations 710 — 205 — 915 — Foreign government obligations 478 22 — — 478 22 Temporarily impaired investment securities held-to-maturity 9,902 52 12,439 102 22,341 154 Total temporarily impaired investment securities $ 117,326 $ 558 $ 110,614 $ 1,364 $ 227,940 $ 1,922 At December 31, 2018 Less than Twelve Months Twelve Months or Longer Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (In Thousands) Investment securities available-for-sale: GSE debentures $ 25,780 $ 191 $ 130,284 $ 2,901 $ 156,064 $ 3,092 GSE CMOs — — 102,630 4,250 102,630 4,250 GSE MBSs 21,487 113 138,051 4,256 159,538 4,369 SBA commercial loan asset-backed securities — — 51 — 51 — Corporate debt obligations 10,019 93 29,689 817 39,708 910 U.S. Treasury bonds 3,927 37 4,753 104 8,680 141 Temporarily impaired investment securities available-for-sale 61,213 434 405,458 12,328 466,671 12,762 Investment securities held-to-maturity: GSE debentures — — 40,653 967 40,653 967 GSEs MBSs — — 11,080 295 11,080 295 Municipal obligations 14,813 107 35,058 609 49,871 716 Foreign government obligations — — 500 — 500 — Temporarily impaired investment securities held-to-maturity 14,813 107 87,291 1,871 102,104 1,978 Total temporarily impaired investment securities $ 76,026 $ 541 $ 492,749 $ 14,199 $ 568,775 $ 14,740
Schedule of maturities of the investments in debt securities	The final stated maturities of the debt securities are as follows for the periods indicated: At December 31, 2019 2018 Amortized Cost Estimated Fair Value Weighted Average Rate Amortized Cost Estimated Fair Value Weighted Average Rate (Dollars in Thousands) Investment securities available-for-sale: Within 1 year $ 12,797 $ 12,804 1.76% $ 12,041 $ 12,007 2.03% After 1 year through 5 years 217,569 220,757 2.19% 195,701 192,692 2.14% After 5 years through 10 years 93,805 94,212 2.04% 115,665 112,819 2.18% Over 10 years 171,994 171,222 2.12% 191,843 185,275 2.17% $ 496,165 $ 498,995 2.13% $ 515,250 $ 502,793 2.16% Investment securities held-to-maturity: Within 1 year $ 6,366 $ 6,381 1.33% $ 7,640 $ 7,618 1.17% After 1 year through 5 years 63,898 64,559 1.81% 72,735 71,492 1.84% After 5 years through 10 years 7,177 7,364 1.79% 23,025 22,640 2.20% Over 10 years 9,339 9,257 1.90% 11,376 11,080 2.13% $ 86,780 $ 87,561 1.82% $ 114,776 $ 112,830 1.89%
Schedule of sales of investment securities	Sales of investment and restricted equity securities are summarized as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Proceeds from sales of debt securities $ — $ 20,000 $ — Proceeds from sales of marketable and restricted equity securities 1,212 2,700 11,393 Gross gains from sales — 1,472 11,612 Gross losses from sales (232 ) (68 ) (219 ) Gain on sales of securities, net $ (232 ) $ 1,404 $ 11,393

Restricted Equity Securities (T

Restricted Equity Securities (Tables)	12 Months Ended
	Dec. 31, 2019
Restricted Investments Note [Abstract]
Components of investments in the restricted equity securities of various entities	Investments in the restricted equity securities of various entities are as follows: At December 31, 2019 2018 (In Thousands) FHLBB stock $ 35,482 $ 43,655 FRB stock 18,084 17,995 Other restricted equity securities 252 101 $ 53,818 $ 61,751

Loans and Leases (Tables)

Loans and Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Receivables [Abstract]
Summary of loan and lease balances for the originated and acquired portfolios	The following tables present loan and lease balances and weighted average coupon rates for the originated and acquired loan and lease portfolios at the dates indicated: At December 31, 2019 Originated Acquired Total Balance Weighted Average Coupon Balance Weighted Average Coupon Balance Weighted Average Coupon (Dollars In Thousands) Commercial real estate loans: Commercial real estate $ 2,400,037 4.32 % $ 90,974 4.63 % $ 2,491,011 4.33 % Multi-family mortgage 896,482 4.18 % 35,681 4.59 % 932,163 4.20 % Construction 239,015 5.04 % 7,033 6.73 % 246,048 5.09 % Total commercial real estate loans 3,535,534 4.33 % 133,688 4.73 % 3,669,222 4.34 % Commercial loans and leases: Commercial 713,875 4.65 % 15,627 5.14 % 729,502 4.66 % Equipment financing 1,049,997 7.71 % 2,411 5.98 % 1,052,408 7.71 % Condominium association 56,838 4.84 % — — % 56,838 4.84 % Total commercial loans and leases 1,820,710 6.42 % 18,038 5.25 % 1,838,748 6.41 % Consumer loans: Residential mortgage 711,522 4.06 % 102,723 4.40 % 814,245 4.10 % Home equity 343,247 4.41 % 33,572 4.93 % 376,819 4.46 % Other consumer 38,674 4.44 % 108 17.91 % 38,782 4.48 % Total consumer loans 1,093,443 4.18 % 136,403 4.54 % 1,229,846 4.22 % Total loans and leases $ 6,449,687 4.89 % $ 288,129 4.67 % $ 6,737,816 4.88 % At December 31, 2018 Originated Acquired Total Balance Weighted Average Coupon Balance Weighted Average Coupon Balance Weighted Average Coupon (Dollars In Thousands) Commercial real estate loans: Commercial real estate $ 2,208,904 4.61 % $ 121,821 4.62 % $ 2,330,725 4.61 % Multi-family mortgage 799,813 4.51 % 47,898 4.58 % 847,711 4.51 % Construction 151,138 5.62 % 22,162 6.74 % 173,300 5.76 % Total commercial real estate loans 3,159,855 4.63 % 191,881 4.85 % 3,351,736 4.64 % Commercial loans and leases: Commercial 712,630 4.96 % 23,788 5.39 % 736,418 4.97 % Equipment financing 978,840 7.61 % 3,249 5.97 % 982,089 7.60 % Condominium association 50,451 4.70 % — — % 50,451 4.70 % Total commercial loans and leases 1,741,921 6.44 % 27,037 5.46 % 1,768,958 6.43 % Consumer loans: Residential mortgage 653,059 4.09 % 129,909 4.45 % 782,968 4.15 % Home equity 331,014 5.05 % 45,470 5.39 % 376,484 5.09 % Other consumer 23,260 5.55 % 110 17.81 % 23,370 5.61 % Total consumer loans 1,007,333 4.44 % 175,489 4.70 % 1,182,822 4.48 % Total loans and leases $ 5,909,109 5.13 % $ 394,407 4.83 % $ 6,303,516 5.11 %
Schedule of activity in the accretable yield for acquired loan portfolio	The following table summarizes activity in the accretable yield for the acquired loan portfolio for the periods indicated: Year Ended December 31, 2019 2018 2017 (In Thousands) Balance at beginning of year $ 7,905 $ 10,522 $ 14,353 Accretion (3,769 ) (4,117 ) (7,801 ) Reclassification from nonaccretable difference as a result from changes in expected cash flows 1,086 1,500 3,970 Balance at end of year $ 5,222 $ 7,905 $ 10,522
Summary of the change in the total amounts of loans and advances, all of which were performing, to directors, executive officers and their affiliates	The following table summarizes the change in the total amounts of loans and advances, to directors, executive officers and their affiliates for the periods indicated. All loans were performing as of December 31, 2019 . Year Ended December 31, 2019 2018 (In Thousands) Balance at beginning of year $ 46,771 $ 47,941 New loans granted during the year 34 2,842 Loans reclassified as insider loans 16,800 — Advances on lines of credit 8,652 193 Repayments (1,857 ) (4,205 ) Balance at end of year $ 70,400 $ 46,771

Allowance for Loan and Lease _2

Allowance for Loan and Lease Losses (Tables)	12 Months Ended
	Dec. 31, 2019
Receivables [Abstract]
Schedule of changes in the allowance for loan and lease losses	The following tables present the changes in the allowance for loan and lease losses and the recorded investment in loans and leases by portfolio segment for the periods indicated: Year Ended December 31, 2019 Commercial Real Estate Commercial Consumer Total (In Thousands) Balance at December 31, 2018 $ 28,187 $ 25,283 $ 5,222 $ 58,692 Charge-offs — (8,911 ) (127 ) (9,038 ) Recoveries — 1,688 179 1,867 Provision for loan and lease losses 2,098 6,766 697 9,561 Balance at December 31, 2019 $ 30,285 $ 24,826 $ 5,971 $ 61,082 Year Ended December 31, 2018 Commercial Real Estate Commercial Consumer Total (In Thousands) Balance at December 31, 2017 $ 27,112 $ 26,333 $ 5,147 $ 58,592 Charge-offs (103 ) (6,585 ) (540 ) (7,228 ) Recoveries — 2,287 290 2,577 Provision for loan and lease losses 1,178 3,248 325 4,751 Balance at December 31, 2018 $ 28,187 $ 25,283 $ 5,222 $ 58,692 Year Ended December 31, 2017 Commercial Real Estate Commercial Consumer Total (In Thousands) Balance at December 31, 2016 $ 27,645 $ 20,906 $ 5,115 $ 53,666 Charge-offs (494 ) (14,914 ) (403 ) (15,811 ) Recoveries 476 1,158 319 1,953 (Credit) provision for loan and lease losses (515 ) 19,183 116 18,784 Balance at December 31, 2017 $ 27,112 $ 26,333 $ 5,147 $ 58,592
Provisions for credit losses	The provisions for credit losses are set forth below for the periods indicated: Originated Acquired Total Year Ended December 31, Year Ended December 31, Year Ended December 31, 2019 2018 2017 2019 2018 2017 2019 2018 2017 (In Thousands) Provision (credit) for loan and lease losses: Commercial real estate $ 1,798 $ 254 $ (343 ) $ 300 $ 924 $ (172 ) $ 2,098 $ 1,178 $ (515 ) Commercial 6,539 3,699 18,899 227 (451 ) 284 6,766 3,248 19,183 Consumer 713 556 273 (16 ) (231 ) (157 ) 697 325 116 Total provision (credit) for loan and lease losses 9,050 4,509 18,829 511 242 (45 ) 9,561 4,751 18,784 Unfunded credit commitments 22 200 204 — — — 22 200 204 Total provision (credit) for credit losses $ 9,072 $ 4,709 $ 19,033 $ 511 $ 242 $ (45 ) $ 9,583 $ 4,951 $ 18,988
Summary of the recorded investments by credit quality indicator, by loan class	The following tables present the recorded investment in loans in each class as of December 31, 2019 by credit quality indicator. At December 31, 2019 Commercial Real Estate Multi- Family Mortgage Construction Commercial Equipment Financing Condominium Association Other Consumer Total (In Thousands) Originated: Loan rating: Pass $ 2,379,925 $ 896,398 $ 239,015 $ 688,268 $ 1,038,793 $ 56,687 $ 38,673 $ 5,337,759 OAEM 17,006 — — 10,803 1,389 — — 29,198 Substandard 3,106 84 — 14,801 7,995 151 1 26,138 Doubtful — — — 3 1,820 — — 1,823 Total originated 2,400,037 896,482 239,015 713,875 1,049,997 56,838 38,674 5,394,918 Acquired: Loan rating: Pass 81,360 35,681 7,033 15,215 2,404 — 108 141,801 OAEM 597 — — 210 — — — 807 Substandard 9,017 — — 202 7 — — 9,226 Total acquired 90,974 35,681 7,033 15,627 2,411 — 108 151,834 Total loans $ 2,491,011 $ 932,163 $ 246,048 $ 729,502 $ 1,052,408 $ 56,838 $ 38,782 $ 5,546,752 As of December 31, 2019 , there were no loans categorized as definite loss. At December 31, 2019 Residential Mortgage Home Equity ($ In Thousands) Originated: Loan-to-value ratio: Less than 50% $ 184,628 22.7 % $ 132,736 35.2 % 50% - 69% 293,976 36.1 % 91,681 24.3 % 70% - 79% 204,600 25.1 % 81,459 21.6 % 80% and over 25,664 3.2 % 37,371 9.9 % Data not available* 2,654 0.3 % — — % Total originated 711,522 87.4 % 343,247 91.0 % Acquired: Loan-to-value ratio: Less than 50% 32,838 4.0 % 16,882 4.5 % 50%—69% 44,754 5.4 % 7,958 2.1 % 70%—79% 14,305 1.8 % 705 0.2 % 80% and over 4,608 0.6 % 4,726 1.3 % Data not available* 6,218 0.8 % 3,301 0.9 % Total acquired 102,723 12.6 % 33,572 9.0 % Total loans $ 814,245 100.0 % $ 376,819 100.0 % _______________________________________________________________________________ * Represents accounts for which data are not available. The following tables present the recorded investment in loans in each class as of December 31, 2018 by credit quality indicator. At December 31, 2018 Commercial Real Estate Multi- Family Mortgage Construction Commercial Equipment Financing Condominium Association Other Consumer Total (In Thousands) Originated: Loan rating: Pass $ 2,198,377 $ 799,483 $ 150,742 $ 685,773 $ 969,275 $ 50,186 $ 23,249 $ 4,877,085 OAEM 6,096 — — 3,726 52 — — 9,874 Substandard 4,431 330 396 22,870 6,895 265 11 35,198 Doubtful — — — 261 2,618 — — 2,879 Total originated 2,208,904 799,813 151,138 712,630 978,840 50,451 23,260 4,925,036 Acquired: Loan rating: Pass 111,919 47,715 22,162 23,250 3,240 — 110 208,396 OAEM 626 — — 236 — — — 862 Substandard 9,276 183 — 302 9 — — 9,770 Total acquired 121,821 47,898 22,162 23,788 3,249 — 110 219,028 Total loans $ 2,330,725 $ 847,711 $ 173,300 $ 736,418 $ 982,089 $ 50,451 $ 23,370 $ 5,144,064 As of December 31, 2018 , there were no loans categorized as definite loss. At December 31, 2018 Residential Mortgage Home Equity ($ In Thousands) Originated: Loan-to-value ratio: Less than 50% $ 171,523 21.9 % $ 142,534 37.9 % 50%—69% 287,337 36.7 % 84,423 22.4 % 70%—79% 173,870 22.2 % 73,898 19.6 % 80% and over 19,030 2.4 % 30,129 8.0 % Data not available* 1,299 0.2 % 30 — % Total originated 653,059 83.4 % 331,014 87.9 % Acquired: Loan-to-value ratio: Less than 50% 36,752 4.6 % 24,705 6.6 % 50%—69% 53,788 6.9 % 10,353 2.7 % 70%—79% 26,510 3.4 % 1,000 0.3 % 80% and over 6,701 0.9 % 4,348 1.2 % Data not available* 6,158 0.8 % 5,064 1.3 % Total acquired 129,909 16.6 % 45,470 12.1 % Total loans $ 782,968 100.0 % $ 376,484 100.0 % _______________________________________________________________________________ * Represents accounts for which data are not available.
Information regarding troubled debt restructuring loans	The following table sets forth information regarding troubled debt restructured loans and leases at the dates indicated: At December 31, 2019 At December 31, 2018 (In Thousands) Troubled debt restructurings: On accrual $ 17,076 $ 12,257 On nonaccrual 6,104 8,684 Total troubled debt restructurings $ 23,180 $ 20,941 The following table presents information regarding foreclosed residential real estate property for the periods indicated: At December 31, 2019 At December 31, 2018 (In Thousands) Recorded investment in mortgage loans collateralized by residential real estate property that are in the process of foreclosure $ 110 $ 121
Information regarding the aging of past due loans, by loan class	The following tables present an age analysis of the recorded investment in total loans and leases as of December 31, 2019 and 2018 . At December 31, 2019 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (In Thousands) Originated: Commercial real estate loans: Commercial real estate $ 3,330 $ 2,032 $ 1,606 $ 6,968 $ 2,393,069 $ 2,400,037 $ 51 $ 2,751 Multi-family mortgage 3,559 553 — 4,112 892,370 896,482 — 84 Construction — — — — 239,015 239,015 — — Total commercial real estate loans 6,889 2,585 1,606 11,080 3,524,454 3,535,534 51 2,835 Commercial loans and leases: Commercial 5,010 199 3,875 9,084 704,791 713,875 — 4,707 Equipment financing 3,098 1,558 7,246 11,902 1,038,095 1,049,997 — 9,822 Condominium association 458 — — 458 56,380 56,838 — 151 Total commercial loans and leases 8,566 1,757 11,121 21,444 1,799,266 1,820,710 — 14,680 Consumer loans: Residential mortgage 1,014 — 3 1,017 710,505 711,522 — 753 Home equity 794 501 139 1,434 341,813 343,247 2 276 Other consumer 46 1 1 48 38,626 38,674 — 1 Total consumer loans 1,854 502 143 2,499 1,090,944 1,093,443 2 1,030 Total originated loans and leases $ 17,309 $ 4,844 $ 12,870 $ 35,023 $ 6,414,664 $ 6,449,687 $ 53 $ 18,545 (Continued) At December 31, 2019 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (1) (In Thousands) Acquired: Commercial real estate loans: Commercial real estate $ 539 $ 59 $ 8,989 $ 9,587 $ 81,387 $ 90,974 $ 8,919 $ 94 Multi-family mortgage — — — — 35,681 35,681 — — Construction — — — — 7,033 7,033 — — Total commercial real estate loans 539 59 8,989 9,587 124,101 133,688 8,919 94 Commercial loans and leases: Commercial — — — — 15,627 15,627 — 202 Equipment financing — — 7 7 2,404 2,411 7 — Total commercial loans and leases — — 7 7 18,031 18,038 7 202 Consumer loans: Residential mortgage 35 75 1,090 1,200 101,523 102,723 1,090 — Home equity 430 — 42 472 33,100 33,572 40 620 Other consumer — — — — 108 108 — — Total consumer loans 465 75 1,132 1,672 134,731 136,403 1,130 620 Total acquired loans and leases 1,004 134 10,128 11,266 276,863 288,129 10,056 916 Total loans and leases $ 18,313 $ 4,978 $ 22,998 $ 46,289 $ 6,691,527 $ 6,737,816 $ 10,109 $ 19,461 (1) Loans and leases acquired with deteriorated credit quality are always accruing. At December 31, 2018 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (In Thousands) Originated: Commercial real estate loans: Commercial real estate $ 5,139 $ 896 $ 2,962 $ 8,997 $ 2,199,907 $ 2,208,904 $ 277 $ 3,806 Multi-family mortgage 893 — 145 1,038 798,775 799,813 — 330 Construction 297 — 396 693 150,445 151,138 — 396 Total commercial real estate loans 6,329 896 3,503 10,728 3,149,127 3,159,855 277 4,532 Commercial loans and leases: Commercial 2,021 582 6,244 8,847 703,783 712,630 1,962 6,421 Equipment financing 2,509 650 5,685 8,844 969,996 978,840 12 9,500 Condominium association 320 — — 320 50,131 50,451 — 265 Total commercial loans and leases 4,850 1,232 11,929 18,011 1,723,910 1,741,921 1,974 16,186 Consumer loans: Residential mortgage 400 — 1,597 1,997 651,062 653,059 — 1,842 Home equity 761 25 183 969 330,045 331,014 1 191 Other consumer 51 18 15 84 23,176 23,260 — 17 Total consumer loans 1,212 43 1,795 3,050 1,004,283 1,007,333 1 2,050 Total originated loans and leases $ 12,391 $ 2,171 $ 17,227 $ 31,789 $ 5,877,320 $ 5,909,109 $ 2,252 $ 22,768 (Continued) At December 31, 2018 Past Due Loans and Leases Past Due Greater Than 90 Days and Accruing 31-60 Days 61-90 Days Greater Than 90 Days Total Current Total Loans and Leases Nonaccrual Loans and Leases (In Thousands) Acquired: Commercial real estate loans: Commercial real estate $ — $ 215 $ 9,087 $ 9,302 $ 112,519 $ 121,821 $ 9,018 $ 122 Multi-family mortgage 348 — — 348 47,550 47,898 — — Construction 360 242 — 602 21,560 22,162 — — Total commercial real estate loans 708 457 9,087 10,252 181,629 191,881 9,018 122 Commercial loans and leases: Commercial 124 44 290 458 23,330 23,788 90 200 Equipment financing — — 9 9 3,240 3,249 9 — Total commercial loans and leases 124 44 299 467 26,570 27,037 99 200 Consumer loans: Residential mortgage — 371 2,113 2,484 127,425 129,909 2,113 290 Home equity 191 265 2 458 45,012 45,470 — 717 Other consumer — — — — 110 110 — — Total consumer loans 191 636 2,115 2,942 172,547 175,489 2,113 1,007 Total acquired loans and leases 1,023 1,137 11,501 13,661 380,746 394,407 11,230 1,329 Total loans and leases $ 13,414 $ 3,308 $ 28,728 $ 45,450 $ 6,258,066 $ 6,303,516 $ 13,482 $ 24,097
Impaired loans and leases, by loan and leases class	The following tables include the recorded investment and unpaid principal balances of impaired loans and leases with the related allowance amount, if applicable, for the originated and acquired loan and lease portfolios at the dates indicated. Also presented are the average recorded investments in the impaired loans and leases and the related amount of interest recognized during the period that the impaired loans were impaired. At December 31, 2019 At December 31, 2018 Recorded (1) Unpaid Related Recorded Investment (2) Unpaid Related (In Thousands) Originated: With no related allowance recorded: Commercial real estate $ 3,899 $ 3,892 $ — $ 5,569 $ 5,545 $ — Commercial 28,539 28,533 — 30,927 31,053 — Consumer 2,237 2,223 — 2,989 2,978 — Total originated with no related allowance recorded 34,675 34,648 — 39,485 39,576 — With an allowance recorded: Commercial real estate 68 68 7 396 396 5 Commercial 5,980 6,055 1,672 8,224 8,208 2,961 Consumer 1,224 1,220 70 665 664 89 Total originated with an allowance recorded 7,272 7,343 1,749 9,285 9,268 3,055 Total originated impaired loans and leases 41,947 41,991 1,749 48,770 48,844 3,055 Acquired: With no related allowance recorded: Commercial real estate 12,365 12,366 — 9,538 9,538 — Commercial 437 437 — 531 531 — Consumer 3,516 3,516 — 4,772 4,772 — Total acquired with no related allowance recorded 16,318 16,319 — 14,841 14,841 — With an allowance recorded: Consumer 447 447 40 154 154 26 Total acquired with an allowance recorded 447 447 40 154 154 26 Total acquired impaired loans and leases 16,765 16,766 40 14,995 14,995 26 Total impaired loans and leases $ 58,712 $ 58,757 $ 1,789 $ 63,765 $ 63,839 $ 3,081 __________________________________________________________________________ (1) Includes originated and acquired nonaccrual loans of $18.5 million and $0.9 million , respectively as of December 31, 2019 . Includes originated loans individually and collectively evaluated for impairment of $27.3 million and $14.6 million , respectively as of December 31, 2019 . Includes acquired loans individually and collectively evaluated for impairment of $5.2 million and $11.6 million , respectively as of December 31, 2019 . (2) Includes originated and acquired nonaccrual loans of $22.7 million and $1.3 million , respectively as of December 31, 2018 . Includes originated loans individually and collectively evaluated for impairment of $41.2 million and $7.6 million , respectively as of December 31, 2018 . Includes acquired loans individually and collectively evaluated for impairment of $2.5 million and $12.5 million , respectively as of December 31, 2018 . Year Ended December 31, 2019 December 31, 2018 December 31, 2017 Average Interest Average Interest Average Interest (In Thousands) Originated: With no related allowance recorded: Commercial real estate $ 5,148 $ 110 $ 6,484 $ 87 $ 10,181 $ 277 Commercial 29,759 1,009 26,514 993 24,950 747 Consumer 2,662 42 2,801 54 4,330 58 Total originated with no related allowance recorded 37,569 1,161 35,799 1,134 39,461 1,082 With an allowance recorded: Commercial real estate 269 3 99 — 3,271 162 Commercial 7,125 76 9,026 96 18,382 1 Consumer 946 32 835 11 — — Total originated with an allowance recorded 8,340 111 9,960 107 21,653 163 Total originated impaired loans and leases 45,909 1,272 45,759 1,241 61,114 1,245 Acquired: With no related allowance recorded: Commercial real estate 11,409 163 9,868 7 4,005 55 Commercial 511 11 1,212 16 2,280 31 Consumer 4,298 39 5,061 61 5,295 69 Total acquired with no related allowance recorded 16,218 213 16,141 84 11,580 155 With an allowance recorded: Consumer 302 11 135 4 151 4 Total acquired with an allowance recorded 302 11 135 4 151 4 Total acquired impaired loans and leases 16,520 224 16,276 88 11,731 159 Total impaired loans and leases $ 62,429 $ 1,496 $ 62,035 $ 1,329 $ 72,845 $ 1,404
Schedule of the impaired and non-impaired loans and leases, by loan and leases class	The following tables present information regarding impaired and non-impaired loans and leases at the dates indicated: At December 31, 2019 Commercial Real Estate Commercial Consumer Total (In Thousands) Allowance for Loan and Lease Losses: Originated: Individually evaluated for impairment $ 7 $ 1,672 $ 70 $ 1,749 Collectively evaluated for impairment 28,415 22,853 5,850 57,118 Total originated loans and leases 28,422 24,525 5,920 58,867 Acquired: Individually evaluated for impairment — — 40 40 Collectively evaluated for impairment 65 197 11 273 Acquired with deteriorated credit quality 1,798 104 — 1,902 Total acquired loans and leases 1,863 301 51 2,215 Total allowance for loan and lease losses $ 30,285 $ 24,826 $ 5,971 $ 61,082 Loans and Leases: Originated: Individually evaluated for impairment $ 3,956 $ 20,019 $ 3,326 $ 27,301 Collectively evaluated for impairment 3,531,578 1,800,691 1,090,117 6,422,386 Total originated loans and leases 3,535,534 1,820,710 1,093,443 6,449,687 Acquired: Individually evaluated for impairment 2,942 397 1,841 5,180 Collectively evaluated for impairment 79,465 15,465 110,758 205,688 Acquired with deteriorated credit quality 51,281 2,176 23,804 77,261 Total acquired loans and leases 133,688 18,038 136,403 288,129 Total loans and leases $ 3,669,222 $ 1,838,748 $ 1,229,846 $ 6,737,816 At December 31, 2018 Commercial Real Estate Commercial Consumer Total (In Thousands) Allowance for Loan and Lease Losses: Originated: Individually evaluated for impairment $ 5 $ 2,961 $ 89 $ 3,055 Collectively evaluated for impairment 26,617 22,131 5,075 53,823 Total originated loans and leases 26,622 25,092 5,164 56,878 Acquired: Individually evaluated for impairment — — 26 26 Collectively evaluated for impairment 32 83 20 135 Acquired with deteriorated credit quality 1,533 108 12 1,653 Total acquired loans and leases 1,565 191 58 1,814 Total allowance for loan and lease losses $ 28,187 $ 25,283 $ 5,222 $ 58,692 Loans and Leases: Originated: Individually evaluated for impairment $ 5,610 $ 32,127 $ 3,502 $ 41,239 Collectively evaluated for impairment 3,154,245 1,709,794 1,003,831 5,867,870 Total originated loans and leases 3,159,855 1,741,921 1,007,333 5,909,109 Acquired: Individually evaluated for impairment — 404 2,072 2,476 Collectively evaluated for impairment 121,119 24,094 142,194 287,407 Acquired with deteriorated credit quality 70,762 2,539 31,223 104,524 Total acquired loans and leases 191,881 27,037 175,489 394,407 Total loans and leases $ 3,351,736 $ 1,768,958 $ 1,182,822 $ 6,303,516
Summary of loans restructured or defaulted	The recorded investment in troubled debt restructurings and the associated specific allowances for loan and lease losses, in the originated and acquired loan and lease portfolios, that were modified during the periods indicated, are as follows. At and for the Year Ended December 31, 2019 Recorded Investment Specific Allowance for Loan and Lease Losses Defaulted (1) Number of Loans/ Leases At Modification At End of Period Nonaccrual Loans and Leases Number of Loans/ Leases Recorded Investment (Dollars in Thousands) Originated: Commercial real estate 2 $ 295 $ 290 $ — $ 221 — $ — Commercial 3 6,794 5,457 2,455 1,912 1 1,912 Equipment financing 7 2,774 2,266 — 392 2 365 Residential mortgage 3 868 866 — 96 — — Home equity 3 453 453 — — — — Total originated 18 11,184 9,332 2,455 2,621 3 2,277 Acquired: Construction 1 4,869 2,942 — — — — Residential mortgage 1 297 295 — — — — Home equity 1 134 133 — 133 — — Total acquired 3 5,300 3,370 — 133 — — Total loans and leases 21 $ 16,484 $ 12,702 $ 2,455 $ 2,754 3 $ 2,277 ______________________________________________________________________ (1) Includes loans and leases that have been modified within the past twelve months and subsequently had payment defaults during the period indicated. At and for the Year Ended December 31, 2018 Recorded Investment Specific Allowance for Loan and Lease Losses Defaulted (1) Number of Loans/ Leases At Modification At End of Period Nonaccrual Loans and Leases Number of Loans/ Leases Recorded Investment (Dollars in Thousands) Originated: Commercial real estate 1 $ 673 $ 652 $ — $ 653 — $ — Commercial 10 1,775 1,706 733 1,706 2 1,075 Equipment financing 14 2,510 2,556 37 1,351 — — Residential mortgage 2 550 550 12 341 1 341 Home equity 1 86 83 — — — — Total originated 28 $ 5,594 $ 5,547 $ 782 $ 4,051 3 $ 1,416 Acquired: Home equity 2 249 245 — 245 — — Total acquired 2 249 245 — 245 — — Total loans and leases 30 $ 5,843 $ 5,792 $ 782 $ 4,296 3 $ 1,416 ______________________________________________________________________ (1) Includes loans and leases that have been modified within the past twelve months and subsequently had payment defaults during the period indicated. At and for the Year Ended December 31, 2017 Recorded Investment Specific Allowance for Loan and Lease Losses Defaulted (1) Number of Loans/ Leases At Modification At End of Period Nonaccrual Loans and Leases Number of Loans/ Leases Recorded Investment (Dollars in Thousands) Originated: Commercial real estate 1 $ 189 $ 189 $ — $ — — $ — Commercial 10 7,861 3,911 191 2,189 2 1,361 Equipment financing 16 2,687 2,901 137 1,440 1 188 Total originated 27 10,737 7,001 328 3,629 3 1,549 ______________________________________________________________________ (1) Includes loans and leases that have been modified within the past twelve months and subsequently had payment defaults during the period indicated.
Schedule of troubled debt restructurings by type of modification	The following table sets forth the Company's end-of-period balances for troubled debt restructurings that were modified during the periods indicated, by type of modification. Year Ended December 31, 2019 2018 2017 (In Thousands) Loans with one modification: Extended maturity $ 5,811 $ 1,717 $ 2,810 Adjusted principal — — 19 Adjusted interest rate 252 — — Interest only — — 174 Combination maturity, principal, interest rate 3,624 3,651 1,914 Total loans modified once $ 9,687 $ 5,368 $ 4,917 Loans with more than one modification: Extended maturity $ 3,015 $ — $ 1,910 Combination maturity, principal, interest rate — 424 174 Total loans modified more than once $ 3,015 $ 424 $ 2,084 Total loans modified $ 12,702 $ 5,792 $ 7,001

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of premises and equipment	Premises and equipment consist of the following: At December 31, Estimated Useful Life 2019 2018 (In Thousands) (In Years) Land $ 12,320 $ 12,300 NA Fine art 545 533 NA Computer equipment 11,886 10,488 3 Vehicles 135 126 3 to 5 Core processing system and software 20,748 20,466 3 to 7.5 Furniture, fixtures and equipment 15,393 14,696 5 to 25 Office building and improvements 90,086 87,913 10 to 40 Total 151,113 146,522 Accumulated depreciation and amortization 76,763 70,140 Total premises and equipment $ 74,350 $ 76,382

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of changes in the carrying value of goodwill	The changes in the carrying value of goodwill for the periods indicated were as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Balance at beginning of year $ 160,427 $ 137,890 $ 137,890 Additions — 22,537 — Balance at end of year $ 160,427 $ 160,427 $ 137,890
Schedule of composition of other intangible assets	The following is a summary of the Company's other intangible assets: At December 31, 2019 At December 31, 2018 Gross Accumulated Carrying Gross Accumulated Carrying (In Thousands) Other intangible assets: Core deposits $ 38,294 $ 34,960 $ 3,334 $ 38,294 $ 33,297 $ 4,997 Trade name 1,600 511 1,089 1,600 511 1,089 Trust relationship 1,568 1,568 — 1,568 1,568 — Other intangible 442 442 — 442 442 — Total other intangible assets $ 41,904 $ 37,481 $ 4,423 $ 41,904 $ 35,818 $ 6,086
Schedule of estimated aggregate future amortization expense for intangible assets	The estimated aggregate future amortization expense for other intangible assets for each of the next five years and thereafter is as follows: Year ended December 31: Amount (In Thousands) 2020 $ 1,297 2021 850 2022 494 2023 263 2024 153 Thereafter 277 Total $ 3,334

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of information regarding the Company's investments in affordable housing projects	Further information regarding the Company's investments in affordable housing projects follows: At December 31, 2019 2018 (In Thousands) Investments in affordable housing projects included in other assets $ 29,939 $ 10,895 Unfunded commitments related to affordable housing projects included in other liabilities 20,286 1,115 Investment in affordable housing tax credits 2,042 1,885 Investment in affordable housing tax benefits 540 585 For the year ended December 31, 2019 2018 2017 (In Thousands) Investment amortization included in provision for income taxes $ 2,097 $ 1,916 $ 1,844 Amount recognized as income tax benefit 540 585 623

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Summary of deposits	A summary of deposits follows: December 31, 2019 December 31, 2018 Amount Weighted Average Rate Amount Weighted Average Rate (Dollars in Thousands) Demand checking accounts $ 1,141,578 — % $ 1,033,551 — % NOW accounts 371,380 0.11 % 336,317 0.10 % Savings accounts 613,467 0.46 % 619,961 0.32 % Money market accounts 1,682,005 1.15 % 1,675,050 1.18 % Total core deposit accounts 3,808,430 0.59 % 3,664,879 0.60 % Certificate of deposit accounts maturing: Within six months 730,512 2.24 % 475,303 1.20 % After six months but within 1 year 650,461 2.24 % 562,018 1.40 % After 1 year but within 2 years 495,509 2.26 % 538,435 1.85 % After 2 years but within 3 years 56,508 2.19 % 95,806 2.16 % After 3 years but within 4 years 58,492 2.64 % 46,027 1.73 % After 4 years but within 5 years 29,759 2.58 % 71,556 2.57 % 5+ Years 401 2.19 % 20 1.98 % Total certificate of deposit accounts 2,021,642 2.26 % 1,789,165 1.58 % Total deposits $ 5,830,072 1.17 % $ 5,454,044 0.92 %
Schedule of interest expense on deposit balances	Interest expense on deposit balances is summarized as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Interest-bearing deposits: NOW accounts $ 436 $ 283 $ 225 Savings accounts 2,900 1,804 1,297 Money market accounts 21,206 15,369 8,863 Certificate of deposit accounts 45,073 24,522 12,903 Total interest-bearing deposits $ 69,615 $ 41,978 $ 23,288

Borrowed Funds (Tables)

Borrowed Funds (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of borrowed funds	Borrowed funds are comprised of the following: At December 31, 2019 2018 (In Thousands) Advances from the FHLBB $ 758,469 $ 784,375 Subordinated debentures and notes 83,591 83,433 Other borrowed funds 60,689 52,734 Total borrowed funds $ 902,749 $ 920,542
Schedule of interest expense on borrowed funds	Interest expense on borrowed funds for the periods indicated is as follows: Year Ended December 31, 2019 2018 2017 (In Thousands) Advances from the FHLBB $ 18,701 $ 18,650 $ 11,330 Subordinated debentures and notes 5,206 5,181 5,081 Other borrowed funds 804 385 170 Total interest expense on borrowed funds $ 24,711 $ 24,216 $ 16,581
Schedule of federal home loan bank advances	FHLBB advances mature as follows: At December 31, 2019 2018 Amount Callable Amount Weighted Average Rate Amount Callable Amount Weighted Average Rate (Dollars in Thousands) Within 1 year $ 599,262 $ — 2.27 % $ 603,590 $ — 2.19 % Over 1 year to 2 years 139,762 — 2.12 % 160,073 — 2.64 % Over 2 years to 3 years 3,210 — 0.01 % 580 — 3.07 % Over 3 years to 4 years — — — % 3,214 — 0.03 % Over 4 years to 5 years 4,025 — 3.91 % — — — % Over 5 years 12,210 — 3.28 % 16,918 — 3.45 % $ 758,469 $ — 2.26 % $ 784,375 $ — 2.30 %
Schedule of information concerning repurchase agreements during the period	Information concerning other borrowed funds is as follows for the periods indicated below: Year Ended December 31, 2019 2018 (Dollars In Thousands) Outstanding at end of year $ 60,689 $ 52,734 Average outstanding for the year 79,276 46,079 Maximum outstanding at any month-end 122,776 55,144 Weighted average rate at end of year 0.60 % 0.16 % Weighted average rate paid for the year 1.01 % 0.83 %
Summary of subordinated debentures	The following table summarizes the Company's subordinated debentures and notes at the dates indicated. Carrying Amount Issue Date Rate Maturity Date Next Call Date December 31, 2019 December 31, 2018 (Dollars in Thousands) June 26, 2003 Variable; 3-month LIBOR + 3.10% June 26, 2033 March 25, 2020 $ 4,826 $ 4,803 March 17, 2004 Variable; 3-month LIBOR + 2.79% March 17, 2034 March 16, 2020 4,739 4,704 September 15, 2014 6.0% Fixed-to-Variable; 3-month LIBOR + 3.315% September 15, 2029 September 15, 2024 74,026 73,926 Total $ 83,591 $ 83,433

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Schedule of financial instruments with off-balance sheet risk	Financial instruments with off-balance-sheet risk at the dates indicated follow: At December 31, 2019 2018 (In Thousands) Financial instruments whose contract amounts represent credit risk: Commitments to originate loans and leases: Commercial real estate $ 50,034 $ 76,642 Commercial 78,058 75,713 Residential mortgage 25,998 16,363 Unadvanced portion of loans and leases 808,681 707,997 Unused lines of credit: Home equity 528,251 487,476 Other consumer 25,374 50,404 Other commercial 380 347 Unused letters of credit: Financial standby letters of credit 10,166 11,491 Performance standby letters of credit 4,652 3,075 Commercial and similar letters of credit 3,823 4,573 Loan level derivatives: Receive fixed, pay variable 1,101,193 714,500 Pay fixed, receive variable 1,101,193 714,500 Risk participation-out agreements 235,693 100,531 Risk participation-in agreements 55,281 35,838 Foreign exchange contracts: Buys foreign currency, sells U.S. currency 1,125 6,573 Sells foreign currency, buys U.S. currency 1,230 6,582
Schedule of Lease Cost, Supplemental Cash Flow and Supplemental Balance Sheet Information	At December 31, 2019 (In Thousands) The components of lease expense were as follow: Operating lease cost $ 6,461 Supplemental cash flow information related to leases was as follows: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 6,515 Right-of-use assets obtained in exchange for new lease obligations: Operating leases $ 66 Supplemental balance sheet information related to leases was as follows: Operating Leases Operating lease right-of-use assets $ 24,876 Operating lease liabilities 24,876 Weighted Average Remaining Lease Term Operating leases 7.47 Weighted Average Discount Rate Operating leases 3.2 %
Maturities of Operating Leases	A summary of future minimum rental payments under such leases at the dates indicated follows: Year ended December 31, Minimum Rental Payments (In Thousands) 2020 $ 5,886 2021 5,267 2022 4,577 2023 3,672 2024 2,305 Thereafter 6,163 Total $ 27,870 Less imputed interest (2,994 ) $ 24,876

Earnings per Share (EPS) (Table

Earnings per Share (EPS) (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Reconciliation of basic EPS and diluted EPS	The following table is a reconciliation of basic EPS and diluted EPS: For the year ended December 31, 2019 2018 2017 Basic Fully Diluted Basic Fully Diluted Basic Fully Diluted (Dollars in Thousands, Except Per Share Amounts) Numerator: Net income $ 87,717 $ 87,717 $ 83,062 $ 83,062 $ 50,518 $ 50,518 Denominator: Weighted average shares outstanding 79,679,781 79,679,781 79,669,668 79,669,668 74,459,508 74,459,508 Effect of dilutive securities — 177,140 — 239,583 — 351,900 Adjusted weighted average shares outstanding 79,679,781 79,856,921 79,669,668 79,909,251 74,459,508 74,811,408 EPS $ 1.10 $ 1.10 $ 1.04 $ 1.04 $ 0.68 $ 0.68

Comprehensive Income_(Loss) (Ta

Comprehensive Income/(Loss) (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of changes in accumulated other comprehensive (loss) income by component, net of tax	Changes in accumulated other comprehensive income (loss) by component, net of tax, were as follows for the periods indicated: Year Ended December 31, 2019 Investment Securities Available-for-Sale Postretirement Benefits Accumulated Other Comprehensive Income (Loss) (In Thousands) Balance at December 31, 2018 $ (9,712 ) $ 252 $ (9,460 ) Other comprehensive income (loss) 11,911 (168 ) 11,743 Balance at December 31, 2019 $ 2,199 $ 84 $ 2,283 Year Ended December 31, 2018 Investment Securities Available-for-Sale Postretirement Benefits Accumulated Other Comprehensive Loss (In Thousands) Balance at December 31, 2017 $ (6,113 ) $ 163 $ (5,950 ) Other comprehensive (loss) income (3,599 ) 89 (3,510 ) Reclassification due to adoption of ASU 2018-02 — — — Balance at December 31, 2018 $ (9,712 ) $ 252 $ (9,460 ) Year Ended December 31, 2017 Investment Securities Available-for-Sale Postretirement Benefits Accumulated Other Comprehensive Loss (In Thousands) Balance at December 31, 2016 $ (4,213 ) $ 395 $ (3,818 ) Other comprehensive loss (817 ) (252 ) (1,069 ) Reclassification due to adoption of ASU 2018-02 (1,083 ) 20 (1,063 ) Balance at December 31, 2017 $ (6,113 ) $ 163 $ (5,950 )

Derivatives and Hedging Activ_2

Derivatives and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of fair value and classification of derivative financial instruments on the consolidated balance sheets and the effect of the derivative financial instruments on the consolidated income statements	The following tables presents the Company's customer related derivative positions for the periods indicated below for those derivatives not designated as hedging. Notional Amount Maturing Number of Positions Less than 1 year Less than 2 years Less than 3 years Less than 4 years Thereafter Total Fair Value December 31, 2019 (Dollars In Thousands) Loan level derivatives Receive fixed, pay variable 119 $ 24,777 $ — $ 31,131 $ 16,794 $ 1,028,491 $ 1,101,193 $ 58,102 Pay fixed, receive variable 119 24,777 — 31,131 16,794 1,028,491 1,101,193 58,102 Risk participation-out agreements 40 13,967 — — 7,143 214,583 235,693 1,229 Risk participation-in agreements 7 — — — 19,000 36,281 55,281 283 Foreign exchange contracts Buys foreign currency, sells U.S. currency 16 $ 1,125 $ — $ — $ — $ — $ 1,125 $ 54 Sells foreign currency, buys U.S. currency 18 1,230 — — — — 1,230 53 Notional Amount Maturing Number of Positions Less than 1 year Less than 2 years Less than 3 years Less than 4 years Thereafter Total Fair Value December 31, 2018 (Dollars In Thousands) Loan level derivatives Receive fixed, pay variable 86 $ 1,931 $ 26,419 $ — $ 31,762 $ 654,388 $ 714,500 $ 6,081 Pay fixed, receive variable 86 1,931 26,419 — 31,762 654,388 714,500 6,081 Risk participation-out agreements 26 — 14,892 — — 85,639 100,531 344 Risk participation-in agreements 5 — — — — 35,838 35,838 84 Foreign exchange contracts Buys foreign currency, sells U.S. currency 22 $ 6,573 $ — $ — $ — $ — $ 6,573 $ 123 Sells foreign currency, buys U.S. currency 37 6,582 — — — — 6,582 131 Changes in the fair value are recognized directly in the Company's consolidated statements of income and are included in other non-interest income in the consolidated statements of income. The table below presents the net gain (loss) recognized in income due to changes in the fair value for the year ended December 31, 2019 and 2018 . Year Ended December 31, 2019 2018 (In Thousands) Net gain recognized in income on: Net risk participation agreements 686 205 Foreign exchange contracts (7 ) 1 Total $ 679 $ 206
Schedule of offsetting derivatives and amounts subject to master netting agreements not offset in the audited consolidated balance sheet	The tables below present the offsetting of derivatives and amounts subject to master netting agreements not offset in the consolidated balance sheet at the dates indicated. At December 31, 2019 Gross Gross Amounts Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Gross Amounts Not Offset in the Statement of Financial Position Net Amount Financial Instruments Pledged Cash Collateral Pledged (In Thousands) Asset derivatives Loan level derivatives $ 59,365 $ — $ 59,365 $ — $ 11,900 $ 47,465 Risk participation-out agreements 1,229 — 1,229 — — 1,229 Foreign exchange contracts 54 — 54 — — 54 Total $ 60,648 $ — $ 60,648 $ — $ 11,900 $ 48,748 Liability derivatives Loan level derivatives $ 59,365 $ — $ 59,365 $ 86,521 $ — $ (27,156 ) Risk participation-in agreements 283 — 283 — — 283 Foreign exchange contracts 53 — 53 — — 53 Total $ 59,701 $ — $ 59,701 $ 86,521 $ — $ (26,820 ) At December 31, 2018 Gross Gross Amounts Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Gross Amounts Not Offset in the Statement of Financial Position Net Amount Financial Instruments Pledged Cash Collateral Pledged (In Thousands) Asset derivatives Loan level derivatives $ 22,013 $ — $ 22,013 $ — $ 50 $ 21,963 Risk participation-out agreements 344 — 344 — — 344 Foreign exchange contracts 131 — 131 — — 131 Total $ 22,488 $ — $ 22,488 $ — $ 50 $ 22,438 Liability derivatives Loan level derivatives $ 22,013 $ — $ 22,013 $ 5,877 $ — $ 16,136 Risk participation-in agreements 84 — 84 — — 84 Foreign exchange contracts 123 — 123 — — 123 Total $ 22,220 $ — $ 22,220 $ 5,877 $ — $ 16,343

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of income tax expense	Income tax expense is comprised of the following amounts: Year Ended December 31, 2019 2018 2017 (In Thousands) Current provision: Federal $ 21,706 $ 23,949 $ 27,825 State 6,565 7,693 5,013 Total current provision 28,271 31,642 32,838 Deferred provision (benefit): Federal 701 (4,323 ) 10,209 State (703 ) (1,130 ) 589 Total deferred provision (benefit) (2 ) (5,453 ) 10,798 Total provision for income taxes $ 28,269 $ 26,189 $ 43,636
Schedule of reconciliation of income tax expense	Total provision for income taxes differed from the amounts computed by applying the statutory U.S. federal income tax rate of 21.0% in 2019 , 21.0% in 2018 and 35.0% in 2017 to income before tax expense as a result of the following: Year Ended December 31, 2019 2018 2017 (Dollars In Thousands) Expected income tax expense at statutory federal tax rate $ 24,366 $ 23,675 $ 34,039 State taxes, net of federal income tax benefit 4,837 5,184 3,641 Bank-owned life insurance (216 ) (218 ) (364 ) Tax-exempt interest income (435 ) (487 ) (873 ) Income attributable to noncontrolling interest in subsidiary (11 ) (933 ) (870 ) Merger and acquisition expense — 32 138 Tax Act Adjustment — (707 ) 8,965 Investments in affordable housing projects (369 ) (358 ) (653 ) Other, net 97 1 (387 ) Total provision for income taxes $ 28,269 $ 26,189 $ 43,636 Effective income tax rate 24.4 % 23.2 % 44.9 %
Schedule of the tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities	The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities at the dates indicated are as follows: At December 31, 2019 2018 (In Thousands) Deferred tax assets: Allowance for loan and lease losses $ 16,294 $ 15,936 Right-of-use asset - operating leases 6,450 — Deferred compensation 4,748 4,692 Identified intangible assets and goodwill 4,319 — Supplemental Executive Retirement Plans 3,023 2,846 Unrealized loss on investment securities available-for-sale — 2,737 Net operating loss carryforwards 187 976 Postretirement benefits 458 391 Nonaccrual interest 557 482 Accrued expense — 372 Restricted stock and stock option plans 751 497 Employee stock ownership plan 83 106 Other 733 331 Total gross deferred tax assets 37,603 29,366 Deferred tax liabilities: Operating leases - liability 6,450 — Identified intangible assets and goodwill — 2,428 Deferred loan origination costs, net 3,785 3,537 Depreciation 420 789 Unrealized gain on investment securities available-for-sale 622 — Prepaid expense 110 116 Accrued Expense 122 — Acquisition fair value adjustments 1,077 1,001 Total gross deferred tax liabilities 12,586 7,871 Net deferred tax asset $ 25,017 $ 21,495

Regulatory Capital Requiremen_2

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Schedule of the Company's and the bank's actual and required capital amounts and ratios	Actual Minimum Required for Capital Adequacy Purposes Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer Minimum Required to be Considered “Well-Capitalized” Under Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in Thousands) At December 31, 2019: Brookline Bancorp, Inc. Common equity Tier 1 capital ratio (1) $ 780,962 11.44 % $ 307,197 4.50 % $ 477,861 7.00 % N/A N/A Tier 1 leverage capital ratio (2) 790,527 10.28 % 307,598 4.00 % 307,598 4.00 % N/A N/A Tier 1 risk-based capital ratio (3) 790,527 11.58 % 409,599 6.00 % 580,266 8.50 % N/A N/A Total risk-based capital ratio (4) 927,515 13.59 % 545,999 8.00 % 716,623 10.50 % N/A N/A Brookline Bank Common equity Tier 1 capital ratio (1) $ 513,311 11.44 % $ 201,914 4.50 % $ 314,089 7.00 % $ 291,654 6.50 % Tier 1 leverage capital ratio (2) 513,311 10.42 % 197,048 4.00 % 197,048 4.00 % 246,310 5.00 % Tier 1 risk-based capital ratio (3) 513,311 11.44 % 269,219 6.00 % 381,394 8.50 % 358,959 8.00 % Total risk-based capital ratio (4) 555,474 12.38 % 358,949 8.00 % 471,121 10.50 % 448,687 10.00 % BankRI Common equity Tier 1 capital ratio (1) $ 240,362 11.75 % $ 92,054 4.50 % $ 143,194 7.00 % $ 132,966 6.50 % Tier 1 leverage capital ratio (2) 240,362 9.97 % 96,434 4.00 % 96,434 4.00 % 120,543 5.00 % Tier 1 risk-based capital ratio (3) 240,362 11.75 % 122,738 6.00 % 173,879 8.50 % 163,651 8.00 % Total risk-based capital ratio (4) 258,719 12.65 % 163,617 8.00 % 214,747 10.50 % 204,521 10.00 % First Ipswich Common equity Tier 1 capital ratio (1) $ 41,320 13.45 % $ 13,825 4.50 % $ 21,505 7.00 % $ 19,969 6.50 % Tier 1 leverage capital ratio (2) 41,320 8.80 % 18,782 4.00 % 18,782 4.00 % 23,477 5.00 % Tier 1 risk-based capital ratio (3) 41,320 13.45 % 18,433 6.00 % 26,113 8.50 % 24,577 8.00 % Total risk-based capital ratio (4) 43,762 14.24 % 24,585 8.00 % 32,268 10.50 % 30,732 10.00 % _______________________________________________________________________________ (1) Common equity Tier 1 capital ratio is calculated by dividing common equity Tier 1 capital by risk-weighted assets. The ratio was established as part of the implementation of Basel III, effective January 1, 2015. (2) Tier 1 leverage capital ratio is calculated by dividing Tier 1 capital by average assets. (3) Tier 1 risk-based capital ratio is calculated by dividing Tier 1 capital by risk-weighted assets. (4) Total risk-based capital ratio is calculated by dividing total capital by risk-weighted assets. The following table presents actual and required capital ratios as of December 31, 2018 for the Company and the Banks under the regulatory capital rules then in effect. Actual Minimum Required for Capital Adequacy Purposes Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer Minimum Required to be Considered “Well-Capitalized” Under Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in Thousands) At December 31, 2018: Brookline Bancorp, Inc. Common equity Tier 1 capital ratio (1) $ 745,103 11.94 % $ 280,818 4.50 % $ 436,828 7.00 % N/A N/A Tier 1 leverage capital ratio (2) 765,089 10.58 % 289,259 4.00 % 289,259 4.00 % N/A N/A Tier 1 risk-based capital ratio (3) 765,089 12.26 % 374,432 6.00 % 530,445 8.50 % N/A N/A Total risk-based capital ratio (4) 899,563 14.42 % 499,064 8.00 % 655,022 10.50 % N/A N/A Brookline Bank Common equity Tier 1 capital ratio (1) $ 495,798 12.06 % $ 184,999 4.50 % $ 287,777 7.00 % $ 267,221 6.50 % Tier 1 leverage capital ratio (2) 506,277 11.02 % 183,767 4.00 % 183,767 4.00 % 229,708 5.00 % Tier 1 risk-based capital ratio (3) 506,277 12.32 % 246,563 6.00 % 349,298 8.50 % 328,751 8.00 % Total risk-based capital ratio (4) 545,533 13.27 % 328,882 8.00 % 431,658 10.50 % 411,102 10.00 % BankRI Common equity Tier 1 capital ratio (1) $ 209,670 11.37 % $ 82,983 4.50 % $ 129,084 7.00 % $ 119,864 6.50 % Tier 1 leverage capital ratio (2) 209,670 9.35 % 89,698 4.00 % 89,698 4.00 % 112,123 5.00 % Tier 1 risk-based capital ratio (3) 209,670 11.37 % 110,644 6.00 % 156,745 8.50 % 147,525 8.00 % Total risk-based capital ratio (4) 227,674 12.35 % 147,481 8.00 % 193,569 10.50 % 184,351 10.00 % First Ipswich Common equity Tier 1 capital ratio (1) $ 39,655 13.91 % $ 12,829 4.50 % $ 19,956 7.00 % $ 18,530 6.50 % Tier 1 leverage capital ratio (2) 39,655 9.59 % 16,540 4.00 % 16,540 4.00 % 20,675 5.00 % Tier 1 risk-based capital ratio (3) 39,655 13.91 % 17,105 6.00 % 24,232 8.50 % 22,807 8.00 % Total risk-based capital ratio (4) 42,944 15.06 % 22,812 8.00 % 29,941 10.50 % 28,515 10.00 % _______________________________________________________________________________ (1) Common equity Tier 1 capital ratio is calculated by dividing common equity Tier 1 capital by risk-weighted assets. The ratio was established as part of the implementation of Basel III, effective January 1, 2015. (2) Tier 1 leverage capital ratio is calculated by dividing Tier 1 capital by average assets. (3) Tier 1 risk-based capital ratio is calculated by dividing Tier 1 capital by risk-weighted assets. (4) Total risk-based capital ratio is calculated by dividing total capital by risk-weighted assets.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Reconciliation of Changes in Plan Assets and Benefit Obligation	The following table presents the change in plan assets and change in benefit obligation: Year Ended December 31, 2019 2018 2017 (In Thousands) Change in plan assets: Fair value of plan assets at beginning of year $ — $ — $ — Employer contributions 32 31 19 Benefits paid (32 ) (31 ) (19 ) Fair value of plan assets at end of year $ — $ — $ — Change in benefit obligation: Benefit obligation at beginning of year $ 1,490 $ 1,534 $ 1,135 Service cost 54 70 49 Interest cost 60 59 43 Estimated benefits paid (32 ) (31 ) (19 ) Actuarial loss (gain) 185 (142 ) 326 Benefit obligation at end of year $ 1,757 $ 1,490 $ 1,534 Funded status at end of year $ 1,757 $ 1,490 $ 1,534 Accumulated benefit obligation at end of year $ 1,757 $ 1,490 $ 1,534
Schedule of the components of net periodic postretirement benefit cost and other amounts recognized in other comprehensive income	The following table presents the components of net periodic postretirement benefit cost and other amounts recognized in other comprehensive income: Year Ended December 31, 2019 2018 2017 (In Thousands) Net periodic benefit expense: Service cost $ 54 $ 70 $ 49 Interest cost 60 59 43 Prior service credit (21 ) (21 ) (21 ) Actuarial gain (27 ) — (47 ) Net periodic benefit expense $ 66 $ 108 $ 24 Changes in postretirement benefit obligation recognized in other comprehensive income: Net actuarial (loss) gain (206 ) $ 142 $ (401 ) Prior service credit (21 ) (21 ) (21 ) Total pre-tax changes in postretirement benefit obligation recognized in other comprehensive income $ (227 ) $ 121 $ (422 )
Schedule of effect of 1% change in assumed health care cost trend rates	A 1% change in assumed health care cost trend rates would have the following effects: Year Ended 1% Increase 1% Decrease (In Thousands) Effect on total service and interest cost components of net periodic postretirement benefit costs $ 25 $ (20 ) Effect on the accumulated postretirement benefit obligation 365 (289 )
Activity under recognition and retention plans	The following table presents information about the Company's restricted stock awards as of and for the year ending December 31, 2019 : Restricted Stock Awards Outstanding Weighted Average Price per Share (Dollars in Thousands, Except Per Share Amounts) Restricted Stock Awards: Outstanding at December 31, 2018 390,635 $ 15.21 Granted 212,461 14.25 Vested (175,160 ) 14.46 Forfeited / Canceled (21,486 ) 11.78 Outstanding at December 31, 2019 406,450 $ 15.21 Unrecognized compensation cost $ 3,964 Weighted average remaining recognition period (months) 24
Schedule of stock option activity	Options Outstanding Weighted Average Exercise Price Per Share Aggregate Intrinsic Value Weighted Average Contractual Term (In Years) (Dollars in Thousands, Except Per Share Amounts) Employee Stock Options (1) : Outstanding at December 31, 2018 5,000 $ 9.90 Granted — — Exercised — — Forfeited / Canceled — — Outstanding at December 31, 2019 5,000 $ 9.90 $ 33 0.8 Exercisable at December 31, 2019 5,000 $ 9.90 $ 33 0.8 _____________________________________________________________________________ (1) Options granted pursuant to the Brookline Bancorp, Inc. 2003 Stock Option Plan (the “2003 Stock Option Plan”). The 2003 Stock Option Plan terminated by its terms on October 16, 2013, however, outstanding option awards granted pursuant to the 2003 Stock Option Plan may be exercised for 10 years

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2019
Fair value of assets and liabilities
Schedule of quantitative information about significant unobservable inputs (Level 3) for assets measured at fair value on a recurring basis	The table below presents quantitative information about significant unobservable inputs (Level 3) for assets measured at fair value on a recurring basis at the dates indicated. Fair Value Valuation Technique At December 31, 2019 At December 31, 2018 (Dollars in Thousands) Collateral-dependent impaired loans and leases $ 2,243 $ 11,451 Appraisal of collateral (1) Other real estate owned — 3,054 Appraisal of collateral (1) _______________________________________________________________________________ (1) Fair value is generally determined through independent appraisals of the underlying collateral. The Company may also use another available source of collateral assessment to determine a reasonable estimate of the fair value of the collateral. Appraisals may be adjusted by management for qualitative factors such as economic factors and estimated liquidation expenses. The range of the unobservable inputs used may vary but is generally 0% - 10% on the discount for costs to sell and 0% - 15% on appraisal adjustments.
Summary of the carrying values and estimated fair values	The following table presents the carrying amount, estimated fair value, and placement in the fair value hierarchy of the Company's financial instruments at the dates indicated. This table excludes financial instruments for which the carrying amount approximates fair value. Financial assets for which the fair value approximates carrying value include cash and cash equivalents, restricted equity securities, and accrued interest receivable. Financial liabilities for which the fair value approximates carrying value include non-maturity deposits, short-term borrowings, and accrued interest payable. There were no transfers between levels during 2019 . Fair Value Measurements Carrying Value Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs (In Thousands) At December 31, 2019 Financial assets: Investment securities held-to-maturity: GSE debentures $ 31,228 $ 31,290 $ — $ 31,290 $ — GSE MBSs 9,360 9,279 — 9,279 — Municipal obligations 45,692 46,514 — 46,514 — Foreign government obligations 500 478 — — 478 Loans and leases, net 6,676,734 6,697,583 — — 6,697,583 Restricted equity securities 53,818 53,818 — — 53,818 Financial liabilities: Certificates of deposit 2,021,642 2,026,683 — 2,026,683 — Borrowed funds 902,749 902,670 — 902,670 — At December 31, 2018 Financial assets: Investment securities held-to-maturity: GSE debentures $ 50,546 $ 49,601 $ — $ 49,601 $ — GSE MBSs 11,426 11,131 — 11,131 — Municipal obligations 52,304 51,598 — 51,598 — Foreign government obligations 500 500 — — 500 Loans held-for-sale 3,247 3,247 — 3,247 — Loans and leases, net 6,244,824 6,154,704 — — 6,154,704 Restricted equity securities 61,751 61,751 — — 61,751 Financial liabilities: Certificates of deposit 1,789,165 1,778,860 — 1,778,860 — Borrowed funds 920,542 886,545 — 886,545 —
Recurring basis
Fair value of assets and liabilities
Schedule of assets and liabilities measured at fair value on a recurring and non-recurring basis	The following table set forth the carrying value of assets and liabilities measured at fair value on a recurring basis at December 31, 2019 and 2018 : Carrying Value as of December 31, 2019 Level 1 Level 2 Level 3 Total (In Thousands) Assets: Investment securities available-for-sale: Debt securities: GSE debentures $ — $ 185,803 $ — $ 185,803 GSE CMOs — 85,932 — 85,932 GSE MBSs — 153,343 — 153,343 SBA commercial loan asset-backed securities — 34 — 34 Corporate debt obligations — 28,986 — 28,986 U.S. Treasury bonds — 44,897 — 44,897 Total investment securities available-for-sale $ — $ 498,995 $ — $ 498,995 Equity securities held-for-trading $ 2,569 $ 1,012 $ — $ 3,581 Loan level derivatives — 59,365 — 59,365 Risk participation-out agreements — 1,229 — 1,229 Foreign exchange contracts — 54 — 54 Liabilities: Loan level derivatives $ — $ 59,365 $ — $ 59,365 Risk participation-in agreements — 283 — 283 Foreign exchange contracts — 53 — 53 Carrying Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (In Thousands) Assets: Investment securities available-for-sale: Debt securities: GSE debentures $ — $ 181,079 $ — $ 181,079 GSE CMOs — 103,130 — 103,130 GSE MBSs — 165,089 — 165,089 SBA commercial loan asset-backed securities — 51 — 51 Corporate debt obligations — 39,708 — 39,708 U.S. Treasury bonds — 13,736 — 13,736 Total investment securities available-for-sale $ — $ 502,793 $ — $ 502,793 Equity securities held for trading $ 3,235 $ 972 $ — $ 4,207 Loan level derivatives — 22,013 — 22,013 Risk participation-out agreements — 344 — 344 Foreign exchange contracts — 131 — 131 Liabilities: Loan level derivatives $ — $ 22,013 $ — $ 22,013 Risk participation-in agreements — 84 — 84 Foreign exchange contracts — 123 — 123
Nonrecurring basis
Fair value of assets and liabilities
Schedule of assets and liabilities measured at fair value on a recurring and non-recurring basis	Assets and liabilities measured at fair value on a non-recurring basis as of December 31, 2019 and 2018 are summarized below: Carrying Value as of December 31, 2019 Level 1 Level 2 Level 3 Total (In Thousands) Assets measured at fair value on a non-recurring basis: Collateral-dependent impaired loans and leases $ — $ — $ 2,243 $ 2,243 Repossessed assets — 2,631 — 2,631 Total assets measured at fair value on a non-recurring basis $ — $ 2,631 $ 2,243 $ 4,874 Carrying Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (In Thousands) Assets measured at fair value on a non-recurring basis: Collateral-dependent impaired loans and leases $ — $ — $ 11,451 $ 11,451 OREO — — 3,054 3,054 Repossessed assets — 965 — 965 Total assets measured at fair value on a non-recurring basis $ — $ 965 $ 14,505 $ 15,470

Condensed Parent Company Fina_2

Condensed Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Balance Sheets	Balance Sheets At December 31, 2019 2018 (In Thousands) ASSETS Cash and due from banks $ 35,736 $ 33,663 Short-term investments 33 33 Total cash and cash equivalents 35,769 33,696 Equity securities held-for-trading 2,569 3,235 ESOP loan to Brookline Bank 752 1,002 Intercompany loan to Brookline Bank 30,000 40,000 Restricted equity securities 252 101 Premises and equipment, net 2,403 4,318 Deferred tax asset 1,742 1,499 Investment in subsidiaries, at equity 924,352 864,798 Goodwill 35,267 35,267 Other assets 12,116 5,400 Total assets $ 1,045,222 $ 989,316 LIABILITIES AND STOCKHOLDERS' EQUITY Borrowed funds $ 83,591 $ 83,433 Deferred tax liability — — Accrued expenses and other liabilities 16,025 5,743 Total liabilities 99,616 89,176 Stockholders' equity: Common stock, $0.01 par value; 200,000,000 shares authorized; 85,177,172 shares issued and 85,177,172 shares issued, respectively 852 852 Additional paid-in capital 736,601 755,629 Retained earnings, partially restricted 265,376 212,838 Accumulated other comprehensive loss 2,283 (9,460 ) Treasury stock, at cost; 5,003,127 shares and 5,020,025 shares, respectively (59,073 ) (59,120 ) Unallocated common stock held by ESOP; 79,548 shares and 109,950 shares, respectively (433 ) (599 ) Total stockholders' equity 945,606 900,140 Total liabilities and stockholders' equity $ 1,045,222 $ 989,316
Statements of Income	Statements of Income Year Ended December 31, 2019 2018 2017 (In Thousands) Interest and dividend income: Dividend income from subsidiaries $ — $ — $ 7,317 Marketable and restricted equity securities 147 37 — ESOP loan to Brookline Bank 77 98 120 Intercompany loan to Brookline Bank 1,183 1,722 532 Total interest and dividend income 1,407 1,857 7,969 Interest expense: Borrowed funds 5,274 5,223 5,123 Net interest income (3,867 ) (3,366 ) 2,846 Non-interest income: Gain on securities, net 467 71 — Other — 16 — Total non-interest income 467 87 — Non-interest expense: Compensation and employee benefits (1) (507 ) 345 391 Occupancy 1,589 1,586 1,584 Equipment and data processing (1) (770 ) (798 ) (1,011 ) Directors' fees 461 417 453 Franchise taxes 306 321 180 Insurance 543 534 528 Professional services 548 364 470 Advertising and marketing 31 19 4 Merger and acquisition expense — 452 411 Other (1) (1,139 ) (1,140 ) (1,224 ) Total non-interest expense 1,062 2,100 1,786 Loss before income taxes (4,462 ) (5,379 ) 1,060 Credit for income taxes (969 ) (1,976 ) (1,944 ) Loss before equity in undistributed income of subsidiaries (3,493 ) (3,403 ) 3,004 Equity in undistributed income of subsidiaries 91,210 86,465 47,514 Net income $ 87,717 $ 83,062 $ 50,518 _______________________________________________________________________________ (1) The Parent Company received a net benefit in 2019, 2018 and 2017 from the intercompany allocation of expense that is eliminated in consolidation.
Statements of Cash Flows	Statements of Cash Flows Year Ended December 31, 2019 2018 2017 (In Thousands) Cash flows from operating activities: Net income attributable to parent company $ 87,717 $ 83,062 $ 50,518 Adjustments to reconcile net income to net cash provided from operating activities: Equity in undistributed income of subsidiaries (91,210 ) (86,465 ) (47,514 ) Depreciation of premises and equipment 2,824 3,073 2,856 Amortization of debt issuance costs 100 100 100 Equity securities held-for-trading 666 (3,235 ) — Other operating activities, net 47,296 (31,014 ) (5,885 ) Net cash provided from (used for) operating activities 47,393 (34,479 ) 75 Cash flows from investing activities: Repayment of ESOP loan by Brookline Bank 250 250 250 Pay down (issuance) of intercompany loan to Brookline Bank 10,000 40,000 (80,000 ) Purchase of restricted equity securities (151 ) (1 ) — Purchase of premises and equipment (909 ) (1,359 ) (1,942 ) Net cash provided from (used for) investing activities 9,190 38,890 (81,692 ) Cash flows from financing activities: Proceeds from issuance of common stock — — 81,943 Common stock issued for acquisition — 55,183 — Redemption of noncontrolling interest in subsidiary (18,470 ) — — Payment of dividends to owners of noncontrolling interest in subsidiary (930 ) — — Payment of dividends on common stock (35,110 ) (31,441 ) (27,035 ) Net cash (used for) provided from financing activities (54,510 ) 23,742 54,908 Net increase (decrease) in cash and cash equivalents 2,073 28,153 (26,709 ) Cash and cash equivalents at beginning of year 33,696 5,543 32,252 Cash and cash equivalents at end of year $ 35,769 $ 33,696 $ 5,543 Supplemental disclosures of cash flow information: Acquisition of First Commons Bank, N.A.: Fair value of assets acquired, net of cash and cash equivalents acquired $ — $ 292,025 $ — Fair value of liabilities assumed — 278,988 —

Quarterly Results of Operatio_2

Quarterly Results of Operations (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly results of operations	2019 Quarters Fourth Third Second First (Dollars in Thousands Except Per Share Data) Interest and dividend income $ 87,450 $ 87,906 $ 87,184 $ 85,086 Interest expense 23,519 24,670 24,050 22,087 Net interest income 63,931 63,236 63,134 62,999 Provision for credit losses 3,602 871 3,757 1,353 Net interest income after provision for credit losses 60,329 62,365 59,377 61,646 Loan level derivative income, net 2,494 2,251 1,772 1,745 (Loss) gain on investment securities, net 133 (116 ) 357 134 Gain on sales of loans and leases held-for-sale 309 550 561 289 Other non-interest income 4,820 5,244 4,788 4,462 Amortization of identified intangible assets (420 ) (421 ) (420 ) (402 ) Other non-interest expense (38,395 ) (39,770 ) (39,184 ) (38,469 ) Income before provision for income taxes 29,270 30,103 27,251 29,405 Provision for income taxes 7,087 7,507 6,780 6,895 Net income before noncontrolling interest in subsidiary 22,183 22,596 20,471 22,510 Less net income attributable to noncontrolling interest in subsidiary — — — 43 Net income attributable to Brookline Bancorp, Inc. $ 22,183 $ 22,596 $ 20,471 $ 22,467 Earnings per share: Basic $ 0.28 $ 0.28 $ 0.26 $ 0.28 Diluted 0.28 0.28 0.26 0.28 Average common shares outstanding: Basic 79,682,724 79,700,403 79,669,922 79,658,583 Diluted 79,845,447 79,883,510 79,886,292 79,843,578 Common stock price: High $ 16.83 $ 15.39 $ 15.92 $ 16.23 Low 14.36 13.73 14.35 13.90 Dividends per share $ 0.115 $ 0.110 $ 0.110 $ 0.105 2018 Quarters Fourth Third Second First (Dollars in Thousands Except Per Share Data) Interest and dividend income $ 83,544 $ 80,636 $ 78,074 $ 71,639 Interest expense 20,385 18,304 15,357 12,148 Net interest income 63,159 62,332 62,717 59,491 Provision for credit losses 123 2,717 1,470 641 Net interest income after provision for credit losses 63,036 59,615 61,247 58,850 Loan level derivative income, net 1,811 2,192 571 866 Gain on sales of investment securities, net (692 ) (243 ) — 1,162 Gain on sales of loans and leases held-for-sale 327 535 722 299 Other non-interest income 5,015 4,585 4,233 3,841 Amortization of identified intangible assets (537 ) (537 ) (539 ) (467 ) Other non-interest expense (39,745 ) (36,773 ) (37,163 ) (39,471 ) Income before provision for income taxes 29,215 29,374 29,071 25,080 Provision for income taxes 7,055 6,140 7,342 5,652 Net income before noncontrolling interest in subsidiary 22,160 23,234 21,729 19,428 Less net income attributable to noncontrolling interest in subsidiary 1,022 774 898 795 Net income attributable to Brookline Bancorp, Inc. $ 21,138 $ 22,460 $ 20,831 $ 18,633 Earnings per share: Basic $ 0.26 $ 0.28 $ 0.26 $ 0.24 Diluted 0.26 0.28 0.26 0.24 Average common shares outstanding: Basic 80,258,489 80,315,050 80,184,977 77,879,593 Diluted 80,407,558 80,515,467 80,505,614 78,167,800 Common stock price: High $ 16.97 $ 19.05 $ 19.25 $ 17.05 Low 12.86 16.70 15.90 15.60 Dividends per share $ 0.105 $ 0.100 $ 0.100 $ 0.090

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - Brookline Bank $ in Millions	Jan. 04, 2019USD ($)
Business Acquisition [Line Items]
Percentage of voting interest acquired	15.93%
Payments to acquired additional interest in subsidiaries	$ 35.9

Basis of Presentation (Details)

Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2019USD ($)classbankofficesegment	Dec. 31, 2018USD ($)
Basis of Presentation
Number of full-service banking offices | bank	31
Number of lending offices | office	2
Impairment of restricted securities	$ 0	$ 0
Number of days past due, non-accrual status (in days)	90 days
Period after which a non-accrual loan is restructured (in months)	6 months
Total loans and leases	$ 6,737,816,000	6,303,516,000
BOLI, as percentage of capital plus reserves, maximum, individual carrier (as a percent)	10.00%
BOLI, as percentage of capital plus reserves, maximum, aggregate (as a percent)	25.00%
Number of reportable segments | segment	1
Minimum
Basis of Presentation
Term of operating lease	3 years
Maximum
Basis of Presentation
Term of operating lease	25 years
Taxi Medallion Portfolio
Basis of Presentation
Total loans and leases	$ 10,300,000	13,700,000
Commercial real estate
Basis of Presentation
Number of loan classes within specific portfolio | class	3
Commercial loans
Basis of Presentation
Number of loan classes within specific portfolio | class	3
Total loans and leases	$ 1,838,748,000	$ 1,768,958,000
Consumer Loan
Basis of Presentation
Number of loan classes within specific portfolio | class	3
BankRI
Basis of Presentation
Number of full-service banking offices | bank	20

Cash, Cash Equivalents and Sh_2

Cash, Cash Equivalents and Short-Term Investments (Short-term Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Short-term investments
FRB interest bearing reserve	$ 39,964	$ 34,914
FHLB overnight deposits	4,237	4,628
Federal funds sold	0	2,500
Total short-term investments	$ 44,201	$ 42,042

Cash, Cash Equivalents and Sh_3

Cash, Cash Equivalents and Short-Term Investments (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Average amount required to be held with Federal Reserve Bank	$ 10.5	$ 8.2
Aggregate reserves	$ 53	$ 48

Investment Securities (Summary

Investment Securities (Summary of Available-for-sale and Held-to-maturity Securities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
AFS, debt securities, amortized cost	$ 496,165,000	$ 515,250,000
AFS, debt securities, gross unrealized gains	4,598,000	305,000
AFS, debt securities, gross unrealized losses	1,768,000	12,762,000
AFS, debt securities, estimated fair value	498,995,000	502,793,000
Investment securities held-to-maturity:
HTM, amortized Cost	86,780,000	114,776,000
HTM, gross unrealized gains	935,000	32,000
HTM, gross unrealized losses	154,000	1,978,000
HTM, estimated fair value	87,561,000	112,830,000
Equity securities held-for-trading
Equity securities, gross unrealized gains	561,000
Equity securities held-for-trading	3,581,000	4,207,000
GSE debentures
Debt Securities, Available-for-sale [Line Items]
AFS, debt securities, amortized cost	182,922,000	184,072,000
AFS, debt securities, gross unrealized gains	2,939,000	99,000
AFS, debt securities, gross unrealized losses	58,000	3,092,000
AFS, debt securities, estimated fair value	185,803,000	181,079,000
Investment securities held-to-maturity:
HTM, amortized Cost	31,228,000	50,546,000
HTM, gross unrealized gains	113,000	22,000
HTM, gross unrealized losses	51,000	967,000
HTM, estimated fair value	31,290,000	49,601,000
GSE CMOs
Debt Securities, Available-for-sale [Line Items]
AFS, debt securities, amortized cost	87,001,000	107,363,000
AFS, debt securities, gross unrealized gains	22,000	17,000
AFS, debt securities, gross unrealized losses	1,091,000	4,250,000
AFS, debt securities, estimated fair value	85,932,000	103,130,000
GSE MBSs
Debt Securities, Available-for-sale [Line Items]
AFS, debt securities, amortized cost	153,049,000	169,334,000
AFS, debt securities, gross unrealized gains	797,000	124,000
AFS, debt securities, gross unrealized losses	503,000	4,369,000
AFS, debt securities, estimated fair value	153,343,000	165,089,000
Investment securities held-to-maturity:
HTM, amortized Cost	9,360,000	11,426,000
HTM, gross unrealized gains	0	0
HTM, gross unrealized losses	81,000	295,000
HTM, estimated fair value	9,279,000	11,131,000
SBA commercial loan asset-backed securities
Debt Securities, Available-for-sale [Line Items]
AFS, debt securities, amortized cost	34,000	51,000
AFS, debt securities, gross unrealized gains	0	0
AFS, debt securities, gross unrealized losses	0	0
AFS, debt securities, estimated fair value	34,000	51,000
Municipal obligations
Investment securities held-to-maturity:
HTM, amortized Cost	45,692,000	52,304,000
HTM, gross unrealized gains	822,000	10,000
HTM, gross unrealized losses	0	716,000
HTM, estimated fair value	46,514,000	51,598,000
Corporate debt obligations
Debt Securities, Available-for-sale [Line Items]
AFS, debt securities, amortized cost	28,484,000	40,618,000
AFS, debt securities, gross unrealized gains	502,000	0
AFS, debt securities, gross unrealized losses	0	910,000
AFS, debt securities, estimated fair value	28,986,000	39,708,000
U.S. treasury bonds
Debt Securities, Available-for-sale [Line Items]
AFS, debt securities, amortized cost	44,675,000	13,812,000
AFS, debt securities, gross unrealized gains	338,000	65,000
AFS, debt securities, gross unrealized losses	116,000	141,000
AFS, debt securities, estimated fair value	44,897,000	13,736,000
Foreign government obligations
Investment securities held-to-maturity:
HTM, amortized Cost	500,000	500,000
HTM, gross unrealized gains	0	0
HTM, gross unrealized losses	22,000	0
HTM, estimated fair value	$ 478,000	$ 500,000

Investment Securities (Narrativ

Investment Securities (Narrative) (Details)	Dec. 17, 2019USD ($)shares	Mar. 06, 2018USD ($)shares	Mar. 31, 2018USD ($)	Mar. 31, 2018USD ($)shares	Dec. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security	Dec. 31, 2017USD ($)
Investment [Line Items]
AFS, debt securities, estimated fair value					$ 498,995,000	$ 502,793,000
Debt securities, unrealized gain (loss)					2,800,000	(12,500,000)
AFS, debt securities, unrealized loss position					$ 205,599,000	$ 466,671,000
Percentage of securities in unrealized loss positions, available-for-sale securities					41.20%	92.80%
AFS, debt securities, unrealized loss position, accumulated loss					$ 1,768,000	$ 12,762,000
Investment securities held to maturity, fair value					87,561,000	112,830,000
Net unrealized gain (loss), held-to-maturity securities					800,000	(1,900,000)
Gross unrealized losses, fair value, held-to-maturity securities					$ 22,341,000	$ 102,104,000
Percentage of securities in unrealized loss positions, held-to-maturity securities					25.50%	90.50%
HTM, gross unrealized losses					$ 154,000	$ 1,978,000
Equity securities held-for-trading					3,581,000	4,207,000
Purchases of investment securities held-to-maturity					1,430,000	8,915,000	$ 26,873,000
Investment securities held-to-maturity					86,780,000	114,776,000
Estimated fair value of debt securities have right to call or prepay the obligations					37,600,000	19,100,000
Estimated fair value of debt securities have right to call or prepay the obligations, scheduled maturities within one year					3,000,000	0
Estimated fair value of debt securities have right to call or prepay the obligations, scheduled maturities of after one year through five years					34,600,000	8,400,000
Estimated fair value of debt securities have right to call or prepay the obligations, scheduled maturities of after five years					0
Estimated fair value of debt securities have right to call or prepay the obligations, scheduled maturities after five years through ten years						10,700,000
Estimated fair value of debt securities have right to call or prepay the obligations, scheduled maturities of which is after 10 years						0
Investment owned shares sold | shares	100,000
Loss on marketable equity securities	$ 232,000
Community Bank Systems, Inc. | Brookline Bank
Investment [Line Items]
Investment owned cash proceeds from settlement		$ 600,000
Investment owned shares received form settlement | shares		11,303
Investment owned shares sold | shares		11,303
Gain (loss) on sale of investments		$ 600,000
Longwood Securities | Brookline Bank
Investment [Line Items]
Investment owned shares sold | shares				3
Gain (loss) on sale of investments			$ (100,000)
Investment owned			$ 1,500,000	$ 1,500,000
GSE debt securities excluding specified securities
Investment [Line Items]
AFS, debt securities, estimated fair value					17,400,000	20,600,000
GSE debentures
Investment [Line Items]
AFS, debt securities, estimated fair value					185,803,000	181,079,000
Debt securities, unrealized gain (loss)					2,900,000	(3,000,000)
Investment securities held to maturity, fair value					31,290,000	49,601,000
Net unrealized gain (loss), held-to-maturity securities					100,000	(900,000)
Gross unrealized losses, fair value, held-to-maturity securities					31,300,000	49,600,000
HTM, gross unrealized losses					$ 51,000	$ 967,000
Available for sale number of securities | security					60	60
Number of securities in unrealized loss positions | security					5	51
Payments to acquired AFS debt securities					$ 0	$ 33,900,000
Number of securities | security					10	17
Number of securities in an unrealized loss position | security					4	14
Purchases of investment securities held-to-maturity					$ 0	$ 8,900,000
Investment securities held-to-maturity					31,228,000	50,546,000
GSE CMOs
Investment [Line Items]
AFS, debt securities, estimated fair value					85,900,000	103,100,000
Debt securities, unrealized gain (loss)					$ (1,100,000)	$ (4,200,000)
Available for sale number of securities | security					61	61
Number of securities in unrealized loss positions | security					45	46
Payments to acquired AFS debt securities					$ 0	$ 0
GSE mortgage-related securities
Investment [Line Items]
AFS, debt securities, estimated fair value					153,300,000	165,100,000
Debt securities, unrealized gain (loss)					$ 300,000	$ (4,200,000)
Available for sale number of securities | security					150	162
Number of securities in unrealized loss positions | security					48	93
Payments to acquired AFS debt securities					$ 19,600,000	$ 15,200,000
SBA commercial loan asset-backed securities
Investment [Line Items]
AFS, debt securities, estimated fair value					$ 34,000	$ 51,000
Available for sale number of securities | security					4	4
Number of securities in unrealized loss positions | security					3
Payments to acquired AFS debt securities					$ 0	$ 0
Corporate debt obligations
Investment [Line Items]
AFS, debt securities, estimated fair value					28,986,000	39,708,000
Debt securities, unrealized gain (loss)					$ (500,000)	$ (900,000)
Available for sale number of securities | security					8	11
Number of securities in unrealized loss positions | security					0	11
Payments to acquired AFS debt securities					$ 0	$ 0
U.S. Treasury bonds
Investment [Line Items]
AFS, debt securities, estimated fair value					44,900,000	13,700,000
Debt securities, unrealized gain (loss)					$ 200,000	$ (100,000)
Available for sale number of securities | security					9	7
Number of securities in unrealized loss positions | security					5	2
Payments to acquired AFS debt securities					$ 30,800,000	$ 24,700,000
GSE MBSs
Investment [Line Items]
AFS, debt securities, estimated fair value					153,343,000	165,089,000
Investment securities held to maturity, fair value					9,279,000	11,131,000
Net unrealized gain (loss), held-to-maturity securities					(100,000)	(300,000)
Gross unrealized losses, fair value, held-to-maturity securities					9,300,000	11,100,000
HTM, gross unrealized losses					$ 81,000	$ 295,000
Number of securities | security					8	8
Purchases of investment securities held-to-maturity					$ 0	$ 0
Investment securities held-to-maturity					9,360,000	11,426,000
Municipal obligations
Investment [Line Items]
Investment securities held to maturity, fair value					46,514,000	51,598,000
Gross unrealized losses, fair value, held-to-maturity securities					46,500,000	51,600,000
HTM, gross unrealized losses					$ 0	$ 716,000
Number of securities | security					93	98
Number of securities in an unrealized loss position | security					6	94
Purchases of investment securities held-to-maturity					$ 900,000	$ 0
Investment securities held-to-maturity					45,692,000	52,304,000
Foreign government obligations
Investment [Line Items]
Investment securities held to maturity, fair value					478,000	500,000
Gross unrealized losses, fair value, held-to-maturity securities					500,000	500,000
HTM, gross unrealized losses					$ 22,000	$ 0
Number of securities | security					1	1
Purchases of investment securities held-to-maturity					$ 0	$ 0
Investment securities held-to-maturity					500,000	500,000
Collateral Pledged
Investment [Line Items]
Available for sale securities pledged as collateral					$ 433,600,000	$ 442,500,000

Investment Securities (Other-Th

Investment Securities (Other-Than-Temporary Impairment) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt securities, available for sale:
Less than twelve months, estimated fair value	$ 107,424	$ 61,213
Less than twelve months, unrealized losses	506	434
Twelve months or longer, estimated fair value	98,175	405,458
Twelve months or longer, unrealized losses	1,262	12,328
Total, fair value	205,599	466,671
Total, unrealized losses	1,768	12,762
Investment securities held-to-maturity
Less than twelve months, estimated fair value	9,902	14,813
Less than twelve months, unrealized losses	52	107
Twelve months or longer, estimated fair value	12,439	87,291
Twelve months or longer, unrealized losses	102	1,871
Total, estimated fair value	22,341	102,104
Total, unrealized losses	154	1,978
Available-for-sale Securities and Held-to-maturity Securities [Abstract] (Deprecated 2018-01-31)
Less Than Twelve Months, Estimated Fair Value	117,326	76,026
Less Than Twelve Months, Unrealized Losses	558	541
Twelve Months or Longer, Estimated Fair Value	110,614	492,749
Twelve Months or Longer, Unrealized Losses	1,364	14,199
Total, Estimated Fair Value	227,940	568,775
Total, Unrealized Losses	1,922	14,740
GSE debentures
Debt securities, available for sale:
Less than twelve months, estimated fair value	10,965	25,780
Less than twelve months, unrealized losses	58	191
Twelve months or longer, estimated fair value	0	130,284
Twelve months or longer, unrealized losses	0	2,901
Total, fair value	10,965	156,064
Total, unrealized losses	58	3,092
Investment securities held-to-maturity
Less than twelve months, estimated fair value	8,714	0
Less than twelve months, unrealized losses	30	0
Twelve months or longer, estimated fair value	2,977	40,653
Twelve months or longer, unrealized losses	21	967
Total, estimated fair value	11,691	40,653
Total, unrealized losses	51	967
GSE CMOs
Debt securities, available for sale:
Less than twelve months, estimated fair value	28,659	0
Less than twelve months, unrealized losses	217	0
Twelve months or longer, estimated fair value	55,885	102,630
Twelve months or longer, unrealized losses	874	4,250
Total, fair value	84,544	102,630
Total, unrealized losses	1,091	4,250
GSE MBSs
Debt securities, available for sale:
Less than twelve months, estimated fair value	42,046	21,487
Less than twelve months, unrealized losses	115	113
Twelve months or longer, estimated fair value	42,257	138,051
Twelve months or longer, unrealized losses	388	4,256
Total, fair value	84,303	159,538
Total, unrealized losses	503	4,369
Investment securities held-to-maturity
Less than twelve months, estimated fair value	0	0
Less than twelve months, unrealized losses	0	0
Twelve months or longer, estimated fair value	9,257	11,080
Twelve months or longer, unrealized losses	81	295
Total, estimated fair value	9,257	11,080
Total, unrealized losses	81	295
SBA commercial loan asset-backed securities
Debt securities, available for sale:
Less than twelve months, estimated fair value	0	0
Less than twelve months, unrealized losses	0	0
Twelve months or longer, estimated fair value	33	51
Twelve months or longer, unrealized losses	0	0
Total, fair value	33	51
Total, unrealized losses	0	0
Corporate debt obligations
Debt securities, available for sale:
Less than twelve months, estimated fair value		10,019
Less than twelve months, unrealized losses		93
Twelve months or longer, estimated fair value		29,689
Twelve months or longer, unrealized losses		817
Total, fair value		39,708
Total, unrealized losses		910
U.S. treasury bonds
Debt securities, available for sale:
Less than twelve months, estimated fair value	25,754	3,927
Less than twelve months, unrealized losses	116	37
Twelve months or longer, estimated fair value	0	4,753
Twelve months or longer, unrealized losses	0	104
Total, fair value	25,754	8,680
Total, unrealized losses	116	141
Municipal obligations
Investment securities held-to-maturity
Less than twelve months, estimated fair value	710	14,813
Less than twelve months, unrealized losses	0	107
Twelve months or longer, estimated fair value	205	35,058
Twelve months or longer, unrealized losses	0	609
Total, estimated fair value	915	49,871
Total, unrealized losses	0	716
Foreign government obligations
Investment securities held-to-maturity
Less than twelve months, estimated fair value	478	0
Less than twelve months, unrealized losses	22	0
Twelve months or longer, estimated fair value	0	500
Twelve months or longer, unrealized losses	0	0
Total, estimated fair value	478	500
Total, unrealized losses	$ 22	$ 0

Investment Securities (Portfoli

Investment Securities (Portfolio Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available for Sale, Amortized Cost
Within 1 year	$ 12,797	$ 12,041
After 1 year through 5 years	217,569	195,701
After 5 years through 10 years	93,805	115,665
Over 10 years	171,994	191,843
AFS, debt securities, amortized cost	496,165	515,250
Available for Sale, Estimated Fair Value
Within 1 year	12,804	12,007
After 1 year through 5 years	220,757	192,692
After 5 years through 10 years	94,212	112,819
Over 10 years	171,222	185,275
Total	$ 498,995	$ 502,793
Available for Sale, Weighted Average Rate
Within 1 year (as a percent)	1.76%	2.03%
After 1 year through 5 years (as a percent)	2.19%	2.14%
After 5 years through 10 years (as a percent)	2.04%	2.18%
Over 10 years (as a percent)	2.12%	2.17%
Total (as a percent)	2.13%	2.16%
Held-to-Maturity, Amortized Cost
Within 1 year	$ 6,366	$ 7,640
After 1 year through 5 years	63,898	72,735
After 5 years through 10 years	7,177	23,025
Over 10 years	9,339	11,376
Total	86,780	114,776
Held-to-Maturity, Estimated Fair Value
Within 1 year	6,381	7,618
After 1 year through 5 years	64,559	71,492
After 5 years through 10 years	7,364	22,640
Over 10 years	9,257	11,080
Total	$ 87,561	$ 112,830
Held-to-Maturity, Weighted Average Rate
Within 1 year (as a percent)	1.33%	1.17%
After 1 year through 5 years (as a percent)	1.81%	1.84%
After 5 years through 10 years (as a percent)	1.79%	2.20%
Over 10 years (as a percent)	1.90%	2.13%
Total (as a percent)	1.82%	1.89%

Investment Securities (Security

Investment Securities (Security Sales) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of debt securities	$ 0	$ 20,000
Proceeds from sales of debt securities	0	22,210	$ 0
Proceeds from sales of marketable and restricted equity securities	1,212	2,700	11,393
Gross gains from sales	0	1,472	11,612
Gross losses from sales	(232)	(68)	(219)
Gain on sales of securities, net	$ (232)	$ 1,404	$ 11,393

Restricted Equity Securities (I

Restricted Equity Securities (Investments in Restricted Equity Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Restricted equity securities
Restricted equity securities	$ 53,818	$ 61,751
FHLBB stock
Restricted equity securities
Restricted equity securities	35,482	43,655
FRB stock
Restricted equity securities
Restricted equity securities	18,084	17,995
Other restricted equity securities
Restricted equity securities
Restricted equity securities	$ 252	$ 101

Restricted Equity Securities (N

Restricted Equity Securities (Narrative) (Details)	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2019
FHLBB stock
Investment [Line Items]
Dividend rate (as a percent)	5.87%	6.17%	5.56%

Loans and Leases (Summary of Lo

Loans and Leases (Summary of Loan and Lease Balances and Weighted Average Coupon Rates) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 6,449,687	$ 5,909,109
Originated, Weighted Average Coupon (as a percent)	4.89%	5.13%
Acquired loans	$ 288,129	$ 394,407
Acquired, Weighted Average Coupon (as a percent)	4.67%	4.83%
Total loans and leases	$ 6,737,816	$ 6,303,516
Total, Weighted Average Coupon (as a percent)	4.88%	5.11%
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 2,491,011	$ 2,330,725
Multi-family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	932,163	847,711
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	246,048	173,300
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	729,502	736,418
Equipment financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,052,408	982,089
Condominium association
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	56,838	50,451
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	814,245	782,968
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	376,819	376,484
Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	38,782	23,370
Commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 3,535,534	$ 3,159,855
Originated, Weighted Average Coupon (as a percent)	4.33%	4.63%
Acquired loans	$ 133,688	$ 191,881
Acquired, Weighted Average Coupon (as a percent)	4.73%	4.85%
Total loans and leases	$ 3,669,222	$ 3,351,736
Total, Weighted Average Coupon (as a percent)	4.34%	4.64%
Commercial real estate loans | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 2,400,037	$ 2,208,904
Originated, Weighted Average Coupon (as a percent)	4.32%	4.61%
Acquired loans	$ 90,974	$ 121,821
Acquired, Weighted Average Coupon (as a percent)	4.63%	4.62%
Total loans and leases	$ 2,491,011	$ 2,330,725
Total, Weighted Average Coupon (as a percent)	4.33%	4.61%
Commercial real estate loans | Multi-family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 896,482	$ 799,813
Originated, Weighted Average Coupon (as a percent)	4.18%	4.51%
Acquired loans	$ 35,681	$ 47,898
Acquired, Weighted Average Coupon (as a percent)	4.59%	4.58%
Total loans and leases	$ 932,163	$ 847,711
Total, Weighted Average Coupon (as a percent)	4.20%	4.51%
Commercial real estate loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 239,015	$ 151,138
Originated, Weighted Average Coupon (as a percent)	5.04%	5.62%
Acquired loans	$ 7,033	$ 22,162
Acquired, Weighted Average Coupon (as a percent)	6.73%	6.74%
Total loans and leases	$ 246,048	$ 173,300
Total, Weighted Average Coupon (as a percent)	5.09%	5.76%
Commercial loans and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 1,820,710	$ 1,741,921
Originated, Weighted Average Coupon (as a percent)	6.42%	6.44%
Acquired loans	$ 18,038	$ 27,037
Acquired, Weighted Average Coupon (as a percent)	5.25%	5.46%
Total loans and leases	$ 1,838,748	$ 1,768,958
Total, Weighted Average Coupon (as a percent)	6.41%	6.43%
Commercial loans and leases | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 713,875	$ 712,630
Originated, Weighted Average Coupon (as a percent)	4.65%	4.96%
Acquired loans	$ 15,627	$ 23,788
Acquired, Weighted Average Coupon (as a percent)	5.14%	5.39%
Total loans and leases	$ 729,502	$ 736,418
Total, Weighted Average Coupon (as a percent)	4.66%	4.97%
Commercial loans and leases | Equipment financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 1,049,997	$ 978,840
Originated, Weighted Average Coupon (as a percent)	7.71%	7.61%
Acquired loans	$ 2,411	$ 3,249
Acquired, Weighted Average Coupon (as a percent)	5.98%	5.97%
Total loans and leases	$ 1,052,408	$ 982,089
Total, Weighted Average Coupon (as a percent)	7.71%	7.60%
Commercial loans and leases | Condominium association
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 56,838	$ 50,451
Originated, Weighted Average Coupon (as a percent)	4.84%	4.70%
Acquired loans	$ 0	$ 0
Acquired, Weighted Average Coupon (as a percent)	0.00%	0.00%
Total loans and leases	$ 56,838	$ 50,451
Total, Weighted Average Coupon (as a percent)	4.84%	4.70%
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 1,093,443	$ 1,007,333
Originated, Weighted Average Coupon (as a percent)	4.18%	4.44%
Acquired loans	$ 136,403	$ 175,489
Acquired, Weighted Average Coupon (as a percent)	4.54%	4.70%
Total loans and leases	$ 1,229,846	$ 1,182,822
Total, Weighted Average Coupon (as a percent)	4.22%	4.48%
Consumer loans | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 711,522	$ 653,059
Originated, Weighted Average Coupon (as a percent)	4.06%	4.09%
Acquired loans	$ 102,723	$ 129,909
Acquired, Weighted Average Coupon (as a percent)	4.40%	4.45%
Total loans and leases	$ 814,245	$ 782,968
Total, Weighted Average Coupon (as a percent)	4.10%	4.15%
Consumer loans | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 343,247	$ 331,014
Originated, Weighted Average Coupon (as a percent)	4.41%	5.05%
Acquired loans	$ 33,572	$ 45,470
Acquired, Weighted Average Coupon (as a percent)	4.93%	5.39%
Total loans and leases	$ 376,819	$ 376,484
Total, Weighted Average Coupon (as a percent)	4.46%	5.09%
Consumer loans | Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 38,674	$ 23,260
Originated, Weighted Average Coupon (as a percent)	4.44%	5.55%
Acquired loans	$ 108	$ 110
Acquired, Weighted Average Coupon (as a percent)	17.91%	17.81%
Total loans and leases	$ 38,782	$ 23,370
Total, Weighted Average Coupon (as a percent)	4.48%	5.61%

Loans and Leases (Narrative) (D

Loans and Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unamortized deferred loan origination fees and costs	$ 15.7	$ 15.6
Percentage of loans to aggregate outstanding amount in the greater New York/New Jersey Metropolitan area and northeastern states	28.10%	26.80%
Percentage of loans to aggregate outstanding amount in Other areas of the United States	71.90%	73.20%
Loans and leases pledged as collateral	$ 3,000	$ 3,000
Directors, executive officers and their affiliates
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded commitments on extensions of credit	$ 12.8	$ 5.9

Loans and Leases (Accretable Yi

Loans and Leases (Accretable Yield for the Acquired Loan Portfolio) (Details) - Acquired - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summarized activity in accretable yield for the acquired loan portfolio
Balance at beginning of year	$ 7,905	$ 10,522	$ 14,353
Accretion	(3,769)	(4,117)	(7,801)
Reclassification from nonaccretable difference as a result from changes in expected cash flows	1,086	1,500	3,970
Balance at end of year	$ 5,222	$ 7,905	$ 10,522

Loans and Leases (Loans and Adv

Loans and Leases (Loans and Advances to Directors, Executive Officers and Their Affiliates) (Details) - Directors, executive officers and their affiliates - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Change in the total amounts of loans and advances, all of which were performing
Balance at beginning of year	$ 46,771	$ 47,941
New loans granted during the year	34	2,842
Loans reclassified as insider loans	16,800	0
Advances on lines of credit	8,652	193
Repayments	(1,857)	(4,205)
Balance at end of year	$ 70,400	$ 46,771

Allowance for Loan and Lease _3

Allowance for Loan and Lease Losses (Summary of Changes in the Allowance for Loan and Lease Losses and Recorded Investments by Portfolio Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in allowance for loan losses
Balance at the beginning of the period				$ 58,692				$ 58,592	$ 58,692	$ 58,592	$ 53,666
Charge-offs									(9,038)	(7,228)	(15,811)
Recoveries									1,867	2,577	1,953
Provision for loan and lease losses									9,561	4,751	18,784
Balance at the end of the period	$ 61,082				$ 58,692				61,082	58,692	58,592
Provisions for credit losses
Total provision (credit) for loan and lease losses									9,561	4,751	18,784
Unfunded credit commitments									22	200	204
Total provision (credit) for credit losses	3,602	$ 871	$ 3,757	1,353	123	$ 2,717	$ 1,470	641	9,583	4,951	18,988
Commercial Real Estate
Changes in allowance for loan losses
Balance at the beginning of the period				28,187				27,112	28,187	27,112	27,645
Charge-offs									0	(103)	(494)
Recoveries									0	0	476
Provision for loan and lease losses									2,098	1,178	(515)
Balance at the end of the period	30,285				28,187				30,285	28,187	27,112
Provisions for credit losses
Total provision (credit) for loan and lease losses									2,098	1,178	(515)
Commercial
Changes in allowance for loan losses
Balance at the beginning of the period				25,283				26,333	25,283	26,333	20,906
Charge-offs									(8,911)	(6,585)	(14,914)
Recoveries									1,688	2,287	1,158
Provision for loan and lease losses									6,766	3,248	19,183
Balance at the end of the period	24,826				25,283				24,826	25,283	26,333
Provisions for credit losses
Total provision (credit) for loan and lease losses									6,766	3,248	19,183
Consumer
Changes in allowance for loan losses
Balance at the beginning of the period				$ 5,222				$ 5,147	5,222	5,147	5,115
Charge-offs									(127)	(540)	(403)
Recoveries									179	290	319
Provision for loan and lease losses									697	325	116
Balance at the end of the period	$ 5,971				$ 5,222				5,971	5,222	5,147
Provisions for credit losses
Total provision (credit) for loan and lease losses									697	325	116
Originated
Changes in allowance for loan losses
Provision for loan and lease losses									9,050	4,509	18,829
Provisions for credit losses
Total provision (credit) for loan and lease losses									9,050	4,509	18,829
Unfunded credit commitments									22	200	204
Total provision (credit) for credit losses									9,072	4,709	19,033
Originated | Commercial Real Estate
Changes in allowance for loan losses
Provision for loan and lease losses									1,798	254	(343)
Provisions for credit losses
Total provision (credit) for loan and lease losses									1,798	254	(343)
Originated | Commercial
Changes in allowance for loan losses
Provision for loan and lease losses									6,539	3,699	18,899
Provisions for credit losses
Total provision (credit) for loan and lease losses									6,539	3,699	18,899
Originated | Consumer
Changes in allowance for loan losses
Provision for loan and lease losses									713	556	273
Provisions for credit losses
Total provision (credit) for loan and lease losses									713	556	273
Acquired
Changes in allowance for loan losses
Provision for loan and lease losses									511	242	(45)
Provisions for credit losses
Total provision (credit) for loan and lease losses									511	242	(45)
Unfunded credit commitments									0	0	0
Total provision (credit) for credit losses									511	242	(45)
Acquired | Commercial Real Estate
Changes in allowance for loan losses
Provision for loan and lease losses									300	924	(172)
Provisions for credit losses
Total provision (credit) for loan and lease losses									300	924	(172)
Acquired | Commercial
Changes in allowance for loan losses
Provision for loan and lease losses									227	(451)	284
Provisions for credit losses
Total provision (credit) for loan and lease losses									227	(451)	284
Acquired | Consumer
Changes in allowance for loan losses
Provision for loan and lease losses									(16)	(231)	(157)
Provisions for credit losses
Total provision (credit) for loan and lease losses									$ (16)	$ (231)	$ (157)

Allowance for Loan and Lease _4

Allowance for Loan and Lease Losses (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss [Line Items]
Unfunded credit commitments liability included in other liabilities	$ 1,900,000	$ 1,900,000
Unfunded credit commitments liability charge-off	0	0
Related allowance	1,789,000	3,081,000
Specific allowance for loan and lease losses	1,800,000	3,100,000
General allowance for loan and lease losses	59,300,000	55,600,000
Total troubled debt restructurings	23,180,000	20,941,000
Nonaccrual Loans and Leases	19,461,000	24,097,000
Charge-offs	9,038,000	7,228,000	$ 15,811,000
Increase in general portion of the allowance for loan and lease losses	3,700,000
Decrease in specific allowance for loan and lease losses	(1,300,000)
Increase (decrease) in financing receivable, modifications	(2,300,000)
Financial impact of modification of performing and nonperforming loans	2,000,000	1,200,000	4,800,000
Loans modified to trouble debt restructurings	3,100,000	0	0
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Increase (decrease) in financing receivable, modifications	(3,600,000)
Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Increase (decrease) in financing receivable, modifications	(2,900,000)
Taxi Medallion Portfolio
Financing Receivable, Allowance for Credit Loss [Line Items]
Related allowance	2,100,000	2,500,000
Specific allowance for loan and lease losses	600,000	1,900,000
General allowance for loan and lease losses	1,500,000	600,000
Total troubled debt restructurings	1,000,000	3,700,000
Nonaccrual Loans and Leases	1,300,000	3,700,000
Charge-offs	1,700,000
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Charge-offs	8,911,000	6,585,000	14,914,000
Commercial real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Charge-offs	0	103,000	494,000
Consumer loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Charge-offs	127,000	540,000	$ 403,000
Originated
Financing Receivable, Allowance for Credit Loss [Line Items]
Related allowance	1,749,000	3,055,000
Nonaccrual Loans and Leases	18,545,000	22,768,000
Originated | Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Related allowance	1,672,000	2,961,000
Nonaccrual Loans and Leases	14,680,000	16,186,000
Originated | Commercial loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	4,707,000	6,421,000
Originated | Commercial loans | Equipment financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	9,822,000	9,500,000
Originated | Commercial loans | Condominium association
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	151,000	265,000
Originated | Commercial real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Related allowance	7,000	5,000
Nonaccrual Loans and Leases	2,835,000	4,532,000
Originated | Commercial real estate loans | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	2,751,000	3,806,000
Originated | Commercial real estate loans | Multi-family mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	84,000	330,000
Originated | Commercial real estate loans | Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	0	396,000
Originated | Consumer loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Related allowance	70,000	89,000
Nonaccrual Loans and Leases	1,030,000	2,050,000
Originated | Consumer loans | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	753,000	1,842,000
Originated | Consumer loans | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	276,000	191,000
Originated | Consumer loans | Other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	1,000	17,000
Acquired
Financing Receivable, Allowance for Credit Loss [Line Items]
Related allowance	40,000	26,000
Nonaccrual Loans and Leases	916,000	1,329,000
Acquired | Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	202,000	200,000
Acquired | Commercial loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	202,000	200,000
Acquired | Commercial loans | Equipment financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	0	0
Acquired | Commercial real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	94,000	122,000
Acquired | Commercial real estate loans | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	94,000	122,000
Acquired | Commercial real estate loans | Multi-family mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	0	0
Acquired | Commercial real estate loans | Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	0	0
Acquired | Consumer loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Related allowance	40,000	26,000
Nonaccrual Loans and Leases	620,000	1,007,000
Acquired | Consumer loans | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	0	290,000
Acquired | Consumer loans | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	620,000	717,000
Acquired | Consumer loans | Other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual Loans and Leases	$ 0	$ 0

Allowance for Loan and Lease _5

Allowance for Loan and Lease Losses (Credit Quality Information) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Credit Quality Information
Recorded investment	$ 6,737,816	$ 6,303,516
Originated
Credit Quality Information
Recorded investment	6,449,687	5,909,109
Acquired
Credit Quality Information
Recorded investment	288,129	394,407
Commercial real estate
Credit Quality Information
Recorded investment	2,491,011	2,330,725
Commercial real estate | Originated
Credit Quality Information
Recorded investment	2,400,037	2,208,904
Commercial real estate | Acquired
Credit Quality Information
Recorded investment	90,974	121,821
Commercial real estate | Pass | Originated
Credit Quality Information
Recorded investment	2,379,925	2,198,377
Commercial real estate | Pass | Acquired
Credit Quality Information
Recorded investment	81,360	111,919
Commercial real estate | OAEM | Originated
Credit Quality Information
Recorded investment	17,006	6,096
Commercial real estate | OAEM | Acquired
Credit Quality Information
Recorded investment	597	626
Commercial real estate | Substandard | Originated
Credit Quality Information
Recorded investment	3,106	4,431
Commercial real estate | Substandard | Acquired
Credit Quality Information
Recorded investment	9,017	9,276
Commercial real estate | Doubtful | Originated
Credit Quality Information
Recorded investment	0	0
Multi-family mortgage
Credit Quality Information
Recorded investment	932,163	847,711
Multi-family mortgage | Originated
Credit Quality Information
Recorded investment	896,482	799,813
Multi-family mortgage | Acquired
Credit Quality Information
Recorded investment	35,681	47,898
Multi-family mortgage | Pass | Originated
Credit Quality Information
Recorded investment	896,398	799,483
Multi-family mortgage | Pass | Acquired
Credit Quality Information
Recorded investment	35,681	47,715
Multi-family mortgage | OAEM | Originated
Credit Quality Information
Recorded investment	0	0
Multi-family mortgage | OAEM | Acquired
Credit Quality Information
Recorded investment	0	0
Multi-family mortgage | Substandard | Originated
Credit Quality Information
Recorded investment	84	330
Multi-family mortgage | Substandard | Acquired
Credit Quality Information
Recorded investment	0	183
Multi-family mortgage | Doubtful | Originated
Credit Quality Information
Recorded investment	0	0
Construction
Credit Quality Information
Recorded investment	246,048	173,300
Construction | Originated
Credit Quality Information
Recorded investment	239,015	151,138
Construction | Acquired
Credit Quality Information
Recorded investment	7,033	22,162
Construction | Pass | Originated
Credit Quality Information
Recorded investment	239,015	150,742
Construction | Pass | Acquired
Credit Quality Information
Recorded investment	7,033	22,162
Construction | OAEM | Originated
Credit Quality Information
Recorded investment	0	0
Construction | OAEM | Acquired
Credit Quality Information
Recorded investment	0	0
Construction | Substandard | Originated
Credit Quality Information
Recorded investment	0	396
Construction | Substandard | Acquired
Credit Quality Information
Recorded investment	0	0
Construction | Doubtful | Originated
Credit Quality Information
Recorded investment	0	0
Commercial
Credit Quality Information
Recorded investment	729,502	736,418
Commercial | Originated
Credit Quality Information
Recorded investment	713,875	712,630
Commercial | Acquired
Credit Quality Information
Recorded investment	15,627	23,788
Commercial | Pass | Originated
Credit Quality Information
Recorded investment	688,268	685,773
Commercial | Pass | Acquired
Credit Quality Information
Recorded investment	15,215	23,250
Commercial | OAEM | Originated
Credit Quality Information
Recorded investment	10,803	3,726
Commercial | OAEM | Acquired
Credit Quality Information
Recorded investment	210	236
Commercial | Substandard | Originated
Credit Quality Information
Recorded investment	14,801	22,870
Commercial | Substandard | Acquired
Credit Quality Information
Recorded investment	202	302
Commercial | Doubtful | Originated
Credit Quality Information
Recorded investment	3	261
Equipment financing
Credit Quality Information
Recorded investment	1,052,408	982,089
Equipment financing | Originated
Credit Quality Information
Recorded investment	1,049,997	978,840
Equipment financing | Acquired
Credit Quality Information
Recorded investment	2,411	3,249
Equipment financing | Pass | Originated
Credit Quality Information
Recorded investment	1,038,793	969,275
Equipment financing | Pass | Acquired
Credit Quality Information
Recorded investment	2,404	3,240
Equipment financing | OAEM | Originated
Credit Quality Information
Recorded investment	1,389	52
Equipment financing | OAEM | Acquired
Credit Quality Information
Recorded investment	0	0
Equipment financing | Substandard | Originated
Credit Quality Information
Recorded investment	7,995	6,895
Equipment financing | Substandard | Acquired
Credit Quality Information
Recorded investment	7	9
Equipment financing | Doubtful | Originated
Credit Quality Information
Recorded investment	1,820	2,618
Condominium association
Credit Quality Information
Recorded investment	56,838	50,451
Condominium association | Originated
Credit Quality Information
Recorded investment	56,838	50,451
Condominium association | Acquired
Credit Quality Information
Recorded investment	0	0
Condominium association | Pass | Originated
Credit Quality Information
Recorded investment	56,687	50,186
Condominium association | Pass | Acquired
Credit Quality Information
Recorded investment	0	0
Condominium association | OAEM | Originated
Credit Quality Information
Recorded investment	0	0
Condominium association | OAEM | Acquired
Credit Quality Information
Recorded investment	0	0
Condominium association | Substandard | Originated
Credit Quality Information
Recorded investment	151	265
Condominium association | Substandard | Acquired
Credit Quality Information
Recorded investment	0	0
Condominium association | Doubtful | Originated
Credit Quality Information
Recorded investment	0	0
Other consumer
Credit Quality Information
Recorded investment	38,782	23,370
Other consumer | Originated
Credit Quality Information
Recorded investment	38,674	23,260
Other consumer | Acquired
Credit Quality Information
Recorded investment	108	110
Other consumer | Pass | Originated
Credit Quality Information
Recorded investment	38,673	23,249
Other consumer | Pass | Acquired
Credit Quality Information
Recorded investment	108	110
Other consumer | OAEM | Originated
Credit Quality Information
Recorded investment	0	0
Other consumer | OAEM | Acquired
Credit Quality Information
Recorded investment	0	0
Other consumer | Substandard | Originated
Credit Quality Information
Recorded investment	1	11
Other consumer | Substandard | Acquired
Credit Quality Information
Recorded investment	0	0
Other consumer | Doubtful | Originated
Credit Quality Information
Recorded investment	0	0
Total
Credit Quality Information
Recorded investment		5,144,064
Total | Originated
Credit Quality Information
Recorded investment	5,394,918	4,925,036
Total | Acquired
Credit Quality Information
Recorded investment	151,834	219,028
Total | Pass
Credit Quality Information
Recorded investment	5,546,752
Total | Pass | Originated
Credit Quality Information
Recorded investment	5,337,759	4,877,085
Total | Pass | Acquired
Credit Quality Information
Recorded investment	141,801	208,396
Total | OAEM | Originated
Credit Quality Information
Recorded investment	29,198	9,874
Total | OAEM | Acquired
Credit Quality Information
Recorded investment	807	862
Total | Substandard | Originated
Credit Quality Information
Recorded investment	26,138	35,198
Total | Substandard | Acquired
Credit Quality Information
Recorded investment	9,226	9,770
Total | Doubtful | Originated
Credit Quality Information
Recorded investment	1,823	2,879
Residential mortgage
Credit Quality Information
Recorded investment	$ 814,245	$ 782,968
Percentage of loans to aggregate outstanding amount	100.00%	100.00%
Residential mortgage | Originated
Credit Quality Information
Recorded investment	$ 711,522	$ 653,059
Percentage of loans to aggregate outstanding amount	87.40%	83.40%
Residential mortgage | Acquired
Credit Quality Information
Recorded investment	$ 102,723	$ 129,909
Percentage of loans to aggregate outstanding amount	12.60%	16.60%
Residential mortgage | Loan-to-value ratio, less than 50% | Originated
Credit Quality Information
Recorded investment	$ 184,628	$ 171,523
Percentage of loans to aggregate outstanding amount	22.70%	21.90%
Residential mortgage | Loan-to-value ratio, less than 50% | Acquired
Credit Quality Information
Recorded investment	$ 32,838	$ 36,752
Percentage of loans to aggregate outstanding amount	4.00%	4.60%
Residential mortgage | Loan-to-value ratio, 50% - 69% | Originated
Credit Quality Information
Recorded investment	$ 293,976	$ 287,337
Percentage of loans to aggregate outstanding amount	36.10%	36.70%
Residential mortgage | Loan-to-value ratio, 50% - 69% | Acquired
Credit Quality Information
Recorded investment	$ 44,754	$ 53,788
Percentage of loans to aggregate outstanding amount	5.40%	6.90%
Residential mortgage | Loan-to-value ratio, 70% - 79% | Originated
Credit Quality Information
Recorded investment	$ 204,600	$ 173,870
Percentage of loans to aggregate outstanding amount	25.10%	22.20%
Residential mortgage | Loan-to-value ratio, 70% - 79% | Acquired
Credit Quality Information
Recorded investment	$ 14,305	$ 26,510
Percentage of loans to aggregate outstanding amount	1.80%	3.40%
Residential mortgage | Loan-to-value ratio, 80% and over | Originated
Credit Quality Information
Recorded investment	$ 25,664	$ 19,030
Percentage of loans to aggregate outstanding amount	3.20%	2.40%
Residential mortgage | Loan-to-value ratio, 80% and over | Acquired
Credit Quality Information
Recorded investment	$ 4,608	$ 6,701
Percentage of loans to aggregate outstanding amount	0.60%	0.90%
Residential mortgage | Data not available | Originated
Credit Quality Information
Recorded investment	$ 2,654	$ 1,299
Percentage of loans to aggregate outstanding amount	0.30%	0.20%
Residential mortgage | Data not available | Acquired
Credit Quality Information
Recorded investment	$ 6,218	$ 6,158
Percentage of loans to aggregate outstanding amount	0.80%	0.80%
Home equity
Credit Quality Information
Recorded investment	$ 376,819	$ 376,484
Percentage of loans to aggregate outstanding amount	100.00%	100.00%
Home equity | Originated
Credit Quality Information
Recorded investment	$ 343,247	$ 331,014
Percentage of loans to aggregate outstanding amount	91.00%	87.90%
Home equity | Acquired
Credit Quality Information
Recorded investment	$ 33,572	$ 45,470
Percentage of loans to aggregate outstanding amount	9.00%	12.10%
Home equity | Loan-to-value ratio, less than 50% | Originated
Credit Quality Information
Recorded investment	$ 132,736	$ 142,534
Percentage of loans to aggregate outstanding amount	35.20%	37.90%
Home equity | Loan-to-value ratio, less than 50% | Acquired
Credit Quality Information
Recorded investment	$ 16,882	$ 24,705
Percentage of loans to aggregate outstanding amount	4.50%	6.60%
Home equity | Loan-to-value ratio, 50% - 69% | Originated
Credit Quality Information
Recorded investment	$ 91,681	$ 84,423
Percentage of loans to aggregate outstanding amount	24.30%	22.40%
Home equity | Loan-to-value ratio, 50% - 69% | Acquired
Credit Quality Information
Recorded investment	$ 7,958	$ 10,353
Percentage of loans to aggregate outstanding amount	2.10%	2.70%
Home equity | Loan-to-value ratio, 70% - 79% | Originated
Credit Quality Information
Recorded investment	$ 81,459	$ 73,898
Percentage of loans to aggregate outstanding amount	21.60%	19.60%
Home equity | Loan-to-value ratio, 70% - 79% | Acquired
Credit Quality Information
Recorded investment	$ 705	$ 1,000
Percentage of loans to aggregate outstanding amount	0.20%	0.30%
Home equity | Loan-to-value ratio, 80% and over | Originated
Credit Quality Information
Recorded investment	$ 37,371	$ 30,129
Percentage of loans to aggregate outstanding amount	9.90%	8.00%
Home equity | Loan-to-value ratio, 80% and over | Acquired
Credit Quality Information
Recorded investment	$ 4,726	$ 4,348
Percentage of loans to aggregate outstanding amount	1.30%	1.20%
Home equity | Data not available | Originated
Credit Quality Information
Recorded investment	$ 0	$ 30
Percentage of loans to aggregate outstanding amount	0.00%	0.00%
Home equity | Data not available | Acquired
Credit Quality Information
Recorded investment	$ 3,301	$ 5,064
Percentage of loans to aggregate outstanding amount	0.90%	1.30%

Allowance for Loan and Lease _6

Allowance for Loan and Lease Losses (Foreclosed Residential Real Estate Property) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Recorded investment in mortgage loans collateralized by residential real estate property that are in the process of foreclosure	$ 110	$ 121

Allowance for Loan and Lease _7

Allowance for Loan and Lease Losses (Past Due Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Age analysis of past due loans
Past Due	$ 46,289	$ 45,450
Current	6,691,527	6,258,066
Total Loans and Leases	6,737,816	6,303,516
Loans and Leases Past Due Greater Than 90 Days and Accruing	10,109	13,482
Nonaccrual Loans and Leases	19,461	24,097
Commercial real estate
Age analysis of past due loans
Total Loans and Leases	2,491,011	2,330,725
Multi-family mortgage
Age analysis of past due loans
Total Loans and Leases	932,163	847,711
Construction
Age analysis of past due loans
Total Loans and Leases	246,048	173,300
Commercial
Age analysis of past due loans
Total Loans and Leases	729,502	736,418
Equipment financing
Age analysis of past due loans
Total Loans and Leases	1,052,408	982,089
Condominium association
Age analysis of past due loans
Total Loans and Leases	56,838	50,451
Residential mortgage
Age analysis of past due loans
Total Loans and Leases	814,245	782,968
Home equity
Age analysis of past due loans
Total Loans and Leases	376,819	376,484
Other consumer
Age analysis of past due loans
Total Loans and Leases	38,782	23,370
Commercial real estate loans
Age analysis of past due loans
Total Loans and Leases	3,669,222	3,351,736
Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Total Loans and Leases	2,491,011	2,330,725
Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Total Loans and Leases	932,163	847,711
Commercial real estate loans | Construction
Age analysis of past due loans
Total Loans and Leases	246,048	173,300
Commercial loans and leases
Age analysis of past due loans
Total Loans and Leases	1,838,748	1,768,958
Commercial loans and leases | Commercial
Age analysis of past due loans
Total Loans and Leases	729,502	736,418
Commercial loans and leases | Equipment financing
Age analysis of past due loans
Total Loans and Leases	1,052,408	982,089
Commercial loans and leases | Condominium association
Age analysis of past due loans
Total Loans and Leases	56,838	50,451
Consumer loans
Age analysis of past due loans
Total Loans and Leases	1,229,846	1,182,822
Consumer loans | Residential mortgage
Age analysis of past due loans
Total Loans and Leases	814,245	782,968
Consumer loans | Home equity
Age analysis of past due loans
Total Loans and Leases	376,819	376,484
Consumer loans | Other consumer
Age analysis of past due loans
Total Loans and Leases	38,782	23,370
31-60 days past due
Age analysis of past due loans
Past Due	18,313	13,414
61-90 days past due
Age analysis of past due loans
Past Due	4,978	3,308
Greater than 90 days past due
Age analysis of past due loans
Past Due	22,998	28,728
Originated
Age analysis of past due loans
Past Due	35,023	31,789
Current	6,414,664	5,877,320
Total Loans and Leases	6,449,687	5,909,109
Loans and Leases Past Due Greater Than 90 Days and Accruing	53	2,252
Nonaccrual Loans and Leases	18,545	22,768
Originated | Commercial real estate
Age analysis of past due loans
Total Loans and Leases	2,400,037	2,208,904
Originated | Multi-family mortgage
Age analysis of past due loans
Total Loans and Leases	896,482	799,813
Originated | Construction
Age analysis of past due loans
Total Loans and Leases	239,015	151,138
Originated | Commercial
Age analysis of past due loans
Total Loans and Leases	713,875	712,630
Originated | Equipment financing
Age analysis of past due loans
Total Loans and Leases	1,049,997	978,840
Originated | Condominium association
Age analysis of past due loans
Total Loans and Leases	56,838	50,451
Originated | Residential mortgage
Age analysis of past due loans
Total Loans and Leases	711,522	653,059
Originated | Home equity
Age analysis of past due loans
Total Loans and Leases	343,247	331,014
Originated | Other consumer
Age analysis of past due loans
Total Loans and Leases	38,674	23,260
Originated | Commercial real estate loans
Age analysis of past due loans
Past Due	11,080	10,728
Current	3,524,454	3,149,127
Total Loans and Leases	3,535,534	3,159,855
Loans and Leases Past Due Greater Than 90 Days and Accruing	51	277
Nonaccrual Loans and Leases	2,835	4,532
Originated | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	6,968	8,997
Current	2,393,069	2,199,907
Total Loans and Leases	2,400,037	2,208,904
Loans and Leases Past Due Greater Than 90 Days and Accruing	51	277
Nonaccrual Loans and Leases	2,751	3,806
Originated | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	4,112	1,038
Current	892,370	798,775
Total Loans and Leases	896,482	799,813
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	84	330
Originated | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	693
Current	239,015	150,445
Total Loans and Leases	239,015	151,138
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	0	396
Originated | Commercial loans and leases
Age analysis of past due loans
Past Due	21,444	18,011
Current	1,799,266	1,723,910
Total Loans and Leases	1,820,710	1,741,921
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	1,974
Nonaccrual Loans and Leases	14,680	16,186
Originated | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	9,084	8,847
Current	704,791	703,783
Total Loans and Leases	713,875	712,630
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	1,962
Nonaccrual Loans and Leases	4,707	6,421
Originated | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	11,902	8,844
Current	1,038,095	969,996
Total Loans and Leases	1,049,997	978,840
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	12
Nonaccrual Loans and Leases	9,822	9,500
Originated | Commercial loans and leases | Condominium association
Age analysis of past due loans
Past Due	458	320
Current	56,380	50,131
Total Loans and Leases	56,838	50,451
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	151	265
Originated | Consumer loans
Age analysis of past due loans
Past Due	2,499	3,050
Current	1,090,944	1,004,283
Total Loans and Leases	1,093,443	1,007,333
Loans and Leases Past Due Greater Than 90 Days and Accruing	2	1
Nonaccrual Loans and Leases	1,030	2,050
Originated | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	1,017	1,997
Current	710,505	651,062
Total Loans and Leases	711,522	653,059
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	753	1,842
Originated | Consumer loans | Home equity
Age analysis of past due loans
Past Due	1,434	969
Current	341,813	330,045
Total Loans and Leases	343,247	331,014
Loans and Leases Past Due Greater Than 90 Days and Accruing	2	1
Nonaccrual Loans and Leases	276	191
Originated | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	48	84
Current	38,626	23,176
Total Loans and Leases	38,674	23,260
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	1	17
Originated | 31-60 days past due
Age analysis of past due loans
Past Due	17,309	12,391
Originated | 31-60 days past due | Commercial real estate loans
Age analysis of past due loans
Past Due	6,889	6,329
Originated | 31-60 days past due | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	3,330	5,139
Originated | 31-60 days past due | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	3,559	893
Originated | 31-60 days past due | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	297
Originated | 31-60 days past due | Commercial loans and leases
Age analysis of past due loans
Past Due	8,566	4,850
Originated | 31-60 days past due | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	5,010	2,021
Originated | 31-60 days past due | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	3,098	2,509
Originated | 31-60 days past due | Commercial loans and leases | Condominium association
Age analysis of past due loans
Past Due	458	320
Originated | 31-60 days past due | Consumer loans
Age analysis of past due loans
Past Due	1,854	1,212
Originated | 31-60 days past due | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	1,014	400
Originated | 31-60 days past due | Consumer loans | Home equity
Age analysis of past due loans
Past Due	794	761
Originated | 31-60 days past due | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	46	51
Originated | 61-90 days past due
Age analysis of past due loans
Past Due	4,844	2,171
Originated | 61-90 days past due | Commercial real estate loans
Age analysis of past due loans
Past Due	2,585	896
Originated | 61-90 days past due | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	2,032	896
Originated | 61-90 days past due | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	553	0
Originated | 61-90 days past due | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	0
Originated | 61-90 days past due | Commercial loans and leases
Age analysis of past due loans
Past Due	1,757	1,232
Originated | 61-90 days past due | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	199	582
Originated | 61-90 days past due | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	1,558	650
Originated | 61-90 days past due | Commercial loans and leases | Condominium association
Age analysis of past due loans
Past Due	0	0
Originated | 61-90 days past due | Consumer loans
Age analysis of past due loans
Past Due	502	43
Originated | 61-90 days past due | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	0	0
Originated | 61-90 days past due | Consumer loans | Home equity
Age analysis of past due loans
Past Due	501	25
Originated | 61-90 days past due | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	1	18
Originated | Greater than 90 days past due
Age analysis of past due loans
Past Due	12,870	17,227
Originated | Greater than 90 days past due | Commercial real estate loans
Age analysis of past due loans
Past Due	1,606	3,503
Originated | Greater than 90 days past due | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	1,606	2,962
Originated | Greater than 90 days past due | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	0	145
Originated | Greater than 90 days past due | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	396
Originated | Greater than 90 days past due | Commercial loans and leases
Age analysis of past due loans
Past Due	11,121	11,929
Originated | Greater than 90 days past due | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	3,875	6,244
Originated | Greater than 90 days past due | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	7,246	5,685
Originated | Greater than 90 days past due | Commercial loans and leases | Condominium association
Age analysis of past due loans
Past Due	0	0
Originated | Greater than 90 days past due | Consumer loans
Age analysis of past due loans
Past Due	143	1,795
Originated | Greater than 90 days past due | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	3	1,597
Originated | Greater than 90 days past due | Consumer loans | Home equity
Age analysis of past due loans
Past Due	139	183
Originated | Greater than 90 days past due | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	1	15
Acquired
Age analysis of past due loans
Past Due	11,266	13,661
Current	276,863	380,746
Total Loans and Leases	288,129	394,407
Loans and Leases Past Due Greater Than 90 Days and Accruing	10,056	11,230
Nonaccrual Loans and Leases	916	1,329
Acquired | Commercial real estate
Age analysis of past due loans
Total Loans and Leases	90,974	121,821
Acquired | Multi-family mortgage
Age analysis of past due loans
Total Loans and Leases	35,681	47,898
Acquired | Construction
Age analysis of past due loans
Total Loans and Leases	7,033	22,162
Acquired | Commercial
Age analysis of past due loans
Total Loans and Leases	15,627	23,788
Acquired | Equipment financing
Age analysis of past due loans
Total Loans and Leases	2,411	3,249
Acquired | Condominium association
Age analysis of past due loans
Total Loans and Leases	0	0
Acquired | Residential mortgage
Age analysis of past due loans
Total Loans and Leases	102,723	129,909
Acquired | Home equity
Age analysis of past due loans
Total Loans and Leases	33,572	45,470
Acquired | Other consumer
Age analysis of past due loans
Total Loans and Leases	108	110
Acquired | Commercial real estate loans
Age analysis of past due loans
Past Due	9,587	10,252
Current	124,101	181,629
Total Loans and Leases	133,688	191,881
Loans and Leases Past Due Greater Than 90 Days and Accruing	8,919	9,018
Nonaccrual Loans and Leases	94	122
Acquired | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	9,587	9,302
Current	81,387	112,519
Total Loans and Leases	90,974	121,821
Loans and Leases Past Due Greater Than 90 Days and Accruing	8,919	9,018
Nonaccrual Loans and Leases	94	122
Acquired | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	0	348
Current	35,681	47,550
Total Loans and Leases	35,681	47,898
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	0	0
Acquired | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	602
Current	7,033	21,560
Total Loans and Leases	7,033	22,162
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	0	0
Acquired | Commercial loans and leases
Age analysis of past due loans
Past Due	7	467
Current	18,031	26,570
Total Loans and Leases	18,038	27,037
Loans and Leases Past Due Greater Than 90 Days and Accruing	7	99
Nonaccrual Loans and Leases	202	200
Acquired | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	0	458
Current	15,627	23,330
Total Loans and Leases	15,627	23,788
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	90
Nonaccrual Loans and Leases	202	200
Acquired | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	7	9
Current	2,404	3,240
Total Loans and Leases	2,411	3,249
Loans and Leases Past Due Greater Than 90 Days and Accruing	7	9
Nonaccrual Loans and Leases	0	0
Acquired | Consumer loans
Age analysis of past due loans
Past Due	1,672	2,942
Current	134,731	172,547
Total Loans and Leases	136,403	175,489
Loans and Leases Past Due Greater Than 90 Days and Accruing	1,130	2,113
Nonaccrual Loans and Leases	620	1,007
Acquired | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	1,200	2,484
Current	101,523	127,425
Total Loans and Leases	102,723	129,909
Loans and Leases Past Due Greater Than 90 Days and Accruing	1,090	2,113
Nonaccrual Loans and Leases	0	290
Acquired | Consumer loans | Home equity
Age analysis of past due loans
Past Due	472	458
Current	33,100	45,012
Total Loans and Leases	33,572	45,470
Loans and Leases Past Due Greater Than 90 Days and Accruing	40	0
Nonaccrual Loans and Leases	620	717
Acquired | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	0	0
Current	108	110
Total Loans and Leases	108	110
Loans and Leases Past Due Greater Than 90 Days and Accruing	0	0
Nonaccrual Loans and Leases	0	0
Acquired | 31-60 days past due
Age analysis of past due loans
Past Due	1,004	1,023
Acquired | 31-60 days past due | Commercial real estate loans
Age analysis of past due loans
Past Due	539	708
Acquired | 31-60 days past due | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	539	0
Acquired | 31-60 days past due | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	0	348
Acquired | 31-60 days past due | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	360
Acquired | 31-60 days past due | Commercial loans and leases
Age analysis of past due loans
Past Due	0	124
Acquired | 31-60 days past due | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	0	124
Acquired | 31-60 days past due | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	0	0
Acquired | 31-60 days past due | Consumer loans
Age analysis of past due loans
Past Due	465	191
Acquired | 31-60 days past due | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	35	0
Acquired | 31-60 days past due | Consumer loans | Home equity
Age analysis of past due loans
Past Due	430	191
Acquired | 31-60 days past due | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	0	0
Acquired | 61-90 days past due
Age analysis of past due loans
Past Due	134	1,137
Acquired | 61-90 days past due | Commercial real estate loans
Age analysis of past due loans
Past Due	59	457
Acquired | 61-90 days past due | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	59	215
Acquired | 61-90 days past due | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	0	0
Acquired | 61-90 days past due | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	242
Acquired | 61-90 days past due | Commercial loans and leases
Age analysis of past due loans
Past Due	0	44
Acquired | 61-90 days past due | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	0	44
Acquired | 61-90 days past due | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	0	0
Acquired | 61-90 days past due | Consumer loans
Age analysis of past due loans
Past Due	75	636
Acquired | 61-90 days past due | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	75	371
Acquired | 61-90 days past due | Consumer loans | Home equity
Age analysis of past due loans
Past Due	0	265
Acquired | 61-90 days past due | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	0	0
Acquired | Greater than 90 days past due
Age analysis of past due loans
Past Due	10,128	11,501
Acquired | Greater than 90 days past due | Commercial real estate loans
Age analysis of past due loans
Past Due	8,989	9,087
Acquired | Greater than 90 days past due | Commercial real estate loans | Commercial real estate
Age analysis of past due loans
Past Due	8,989	9,087
Acquired | Greater than 90 days past due | Commercial real estate loans | Multi-family mortgage
Age analysis of past due loans
Past Due	0	0
Acquired | Greater than 90 days past due | Commercial real estate loans | Construction
Age analysis of past due loans
Past Due	0	0
Acquired | Greater than 90 days past due | Commercial loans and leases
Age analysis of past due loans
Past Due	7	299
Acquired | Greater than 90 days past due | Commercial loans and leases | Commercial
Age analysis of past due loans
Past Due	0	290
Acquired | Greater than 90 days past due | Commercial loans and leases | Equipment financing
Age analysis of past due loans
Past Due	7	9
Acquired | Greater than 90 days past due | Consumer loans
Age analysis of past due loans
Past Due	1,132	2,115
Acquired | Greater than 90 days past due | Consumer loans | Residential mortgage
Age analysis of past due loans
Past Due	1,090	2,113
Acquired | Greater than 90 days past due | Consumer loans | Home equity
Age analysis of past due loans
Past Due	42	2
Acquired | Greater than 90 days past due | Consumer loans | Other consumer
Age analysis of past due loans
Past Due	$ 0	$ 0

Allowance for Loan and Lease _8

Allowance for Loan and Lease Losses (Recorded Investment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Impaired Loans and Leases
Recorded investment	$ 58,712	$ 63,765
Unpaid principal balance	58,757	63,839
Related allowance	1,789	3,081
Average recorded investment	62,429	62,035	$ 72,845
Interest income recognized, Total	1,496	1,329	1,404
Recorded investment in loans and leases by portfolio segment
Total, Allowance	61,082	58,692
Total Loans and Leases	6,737,816	6,303,516
Originated
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	34,675	39,485
Recorded investment, loans with related allowance recorded	7,272	9,285
Recorded investment	41,947	48,770
Unpaid principal balance with no related allowance recorded	34,648	39,576
Unpaid principal balance with related allowance recorded	7,343	9,268
Unpaid principal balance	41,991	48,844
Related allowance	1,749	3,055
Recorded investment, nonaccrual loans	18,500	22,700
Individually evaluated for impairment, loans and leases	27,300	41,200
Collectively evaluated for impairment, loans and leases	14,600	7,600
Average recorded investment with no related allowance recorded	37,569	35,799	39,461
Average recorded investment with related allowance recorded	8,340	9,960	21,653
Average recorded investment	45,909	45,759	61,114
Interest income recognized with no related allowance recorded	1,161	1,134	1,082
Interest income recognized with related allowance recorded	111	107	163
Interest income recognized, Total	1,272	1,241	1,245
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	1,749	3,055
Collectively evaluated for impairment, allowance	57,118	53,823
Total, Allowance	58,867	56,878
Individually evaluated for impairment, loans and leases	27,301	41,239
Collectively evaluated for impairment, loans and leases	6,422,386	5,867,870
Total Loans and Leases	6,449,687	5,909,109
Acquired
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	16,318	14,841
Recorded investment, loans with related allowance recorded	447	154
Recorded investment	16,765	14,995
Unpaid principal balance with no related allowance recorded	16,319	14,841
Unpaid principal balance with related allowance recorded	447	154
Unpaid principal balance	16,766	14,995
Related allowance	40	26
Recorded investment, nonaccrual loans	900	1,300
Individually evaluated for impairment, loans and leases	5,200	2,500
Collectively evaluated for impairment, loans and leases	11,600	12,500
Average recorded investment with no related allowance recorded	16,218	16,141	11,580
Average recorded investment with related allowance recorded	302	135	151
Average recorded investment	16,520	16,276	11,731
Interest income recognized with no related allowance recorded	213	84	155
Interest income recognized with related allowance recorded	11	4	4
Interest income recognized, Total	224	88	159
Recorded investment in loans and leases by portfolio segment
Total, Allowance	2,215	1,814
Total Loans and Leases	288,129	394,407
Financial Asset Acquired and No Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	40	26
Collectively evaluated for impairment, allowance	273	135
Individually evaluated for impairment, loans and leases	5,180	2,476
Collectively evaluated for impairment, loans and leases	205,688	287,407
Financial Asset Acquired with Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Total, Allowance	1,902	1,653
Total Loans and Leases	77,261	104,524
Commercial real estate loans
Recorded investment in loans and leases by portfolio segment
Total, Allowance	30,285	28,187
Total Loans and Leases	3,669,222	3,351,736
Commercial real estate loans | Originated
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	3,899	5,569
Recorded investment, loans with related allowance recorded	68	396
Unpaid principal balance with no related allowance recorded	3,892	5,545
Unpaid principal balance with related allowance recorded	68	396
Related allowance	7	5
Average recorded investment with no related allowance recorded	5,148	6,484	10,181
Average recorded investment with related allowance recorded	269	99	3,271
Interest income recognized with no related allowance recorded	110	87	277
Interest income recognized with related allowance recorded	3	0	162
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	7	5
Collectively evaluated for impairment, allowance	28,415	26,617
Total, Allowance	28,422	26,622
Individually evaluated for impairment, loans and leases	3,956	5,610
Collectively evaluated for impairment, loans and leases	3,531,578	3,154,245
Total Loans and Leases	3,535,534	3,159,855
Commercial real estate loans | Acquired
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	12,365	9,538
Unpaid principal balance with no related allowance recorded	12,366	9,538
Average recorded investment with no related allowance recorded	11,409	9,868	4,005
Interest income recognized with no related allowance recorded	163	7	55
Recorded investment in loans and leases by portfolio segment
Total, Allowance	1,863	1,565
Total Loans and Leases	133,688	191,881
Commercial real estate loans | Financial Asset Acquired and No Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	0	0
Collectively evaluated for impairment, allowance	65	32
Individually evaluated for impairment, loans and leases	2,942	0
Collectively evaluated for impairment, loans and leases	79,465	121,119
Commercial real estate loans | Financial Asset Acquired with Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Total, Allowance	1,798	1,533
Total Loans and Leases	51,281	70,762
Commercial
Recorded investment in loans and leases by portfolio segment
Total, Allowance	24,826	25,283
Total Loans and Leases	1,838,748	1,768,958
Commercial | Originated
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	28,539	30,927
Recorded investment, loans with related allowance recorded	5,980	8,224
Unpaid principal balance with no related allowance recorded	28,533	31,053
Unpaid principal balance with related allowance recorded	6,055	8,208
Related allowance	1,672	2,961
Average recorded investment with no related allowance recorded	29,759	26,514	24,950
Average recorded investment with related allowance recorded	7,125	9,026	18,382
Interest income recognized with no related allowance recorded	1,009	993	747
Interest income recognized with related allowance recorded	76	96	1
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	1,672	2,961
Collectively evaluated for impairment, allowance	22,853	22,131
Total, Allowance	24,525	25,092
Individually evaluated for impairment, loans and leases	20,019	32,127
Collectively evaluated for impairment, loans and leases	1,800,691	1,709,794
Total Loans and Leases	1,820,710	1,741,921
Commercial | Acquired
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	437	531
Unpaid principal balance with no related allowance recorded	437	531
Average recorded investment with no related allowance recorded	511	1,212	2,280
Interest income recognized with no related allowance recorded	11	16	31
Recorded investment in loans and leases by portfolio segment
Total, Allowance	301	191
Total Loans and Leases	18,038	27,037
Commercial | Financial Asset Acquired and No Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	0	0
Collectively evaluated for impairment, allowance	197	83
Individually evaluated for impairment, loans and leases	397	404
Collectively evaluated for impairment, loans and leases	15,465	24,094
Commercial | Financial Asset Acquired with Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Total, Allowance	104	108
Total Loans and Leases	2,176	2,539
Consumer loans
Recorded investment in loans and leases by portfolio segment
Total, Allowance	5,971	5,222
Total Loans and Leases	1,229,846	1,182,822
Consumer loans | Originated
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	2,237	2,989
Recorded investment, loans with related allowance recorded	1,224	665
Unpaid principal balance with no related allowance recorded	2,223	2,978
Unpaid principal balance with related allowance recorded	1,220	664
Related allowance	70	89
Average recorded investment with no related allowance recorded	2,662	2,801	4,330
Average recorded investment with related allowance recorded	946	835	0
Interest income recognized with no related allowance recorded	42	54	58
Interest income recognized with related allowance recorded	32	11	0
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	70	89
Collectively evaluated for impairment, allowance	5,850	5,075
Total, Allowance	5,920	5,164
Individually evaluated for impairment, loans and leases	3,326	3,502
Collectively evaluated for impairment, loans and leases	1,090,117	1,003,831
Total Loans and Leases	1,093,443	1,007,333
Consumer loans | Acquired
Impaired Loans and Leases
Recorded investment, loans with no related allowance recorded	3,516	4,772
Recorded investment, loans with related allowance recorded	447	154
Unpaid principal balance with no related allowance recorded	3,516	4,772
Unpaid principal balance with related allowance recorded	447	154
Related allowance	40	26
Average recorded investment with no related allowance recorded	4,298	5,061	5,295
Average recorded investment with related allowance recorded	302	135	151
Interest income recognized with no related allowance recorded	39	61	69
Interest income recognized with related allowance recorded	11	4	$ 4
Recorded investment in loans and leases by portfolio segment
Total, Allowance	51	58
Total Loans and Leases	136,403	175,489
Consumer loans | Financial Asset Acquired and No Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Individually evaluated for impairment, allowance	40	26
Collectively evaluated for impairment, allowance	11	20
Individually evaluated for impairment, loans and leases	1,841	2,072
Collectively evaluated for impairment, loans and leases	110,758	142,194
Consumer loans | Financial Asset Acquired with Credit Deterioration
Recorded investment in loans and leases by portfolio segment
Total, Allowance	0	12
Total Loans and Leases	$ 23,804	$ 31,223

Allowance for Loan and Lease _9

Allowance for Loan and Lease Losses (Troubled Debt Restructurings) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)loan	Dec. 31, 2018USD ($)loan	Dec. 31, 2017USD ($)loan
Receivables [Abstract]
On accrual	$ 17,076	$ 12,257
On nonaccrual	6,104	8,684
Total troubled debt restructurings	$ 23,180	$ 20,941
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	21	30
Recorded Investment, At Modification	$ 16,484	$ 5,843
Recorded Investment, At end of period	12,702	5,792	$ 7,001
Specific Allowance for Loan and Lease Losses	2,455	782
Nonaccrual Loans and Leases	$ 2,754	$ 4,296
Defaulted, number of loans/leases | loan	3	3
Defaulted, recorded investment	$ 2,277	$ 1,416
Loans with one modification	9,687	5,368	4,917
Loans with more than one modification	3,015	424	2,084
Extended maturity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans with one modification	5,811	1,717	2,810
Loans with more than one modification	3,015	0	1,910
Adjusted principal
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans with one modification	0	0	19
Adjusted interest rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans with one modification	252	0	0
Interest only
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans with one modification	0	0	174
Combination maturity, principal, interest rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans with one modification	3,624	3,651	1,914
Loans with more than one modification	$ 0	$ 424	$ 174
Originated
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	18	28	27
Recorded Investment, At Modification	$ 11,184	$ 5,594	$ 10,737
Recorded Investment, At end of period	9,332	5,547	7,001
Specific Allowance for Loan and Lease Losses	2,455	782	328
Nonaccrual Loans and Leases	$ 2,621	$ 4,051	$ 3,629
Defaulted, number of loans/leases | loan	3	3	3
Defaulted, recorded investment	$ 2,277	$ 1,416	$ 1,549
Originated | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	2	1	1
Recorded Investment, At Modification	$ 295	$ 673	$ 189
Recorded Investment, At end of period	290	652	189
Specific Allowance for Loan and Lease Losses	0	0	0
Nonaccrual Loans and Leases	$ 221	$ 653	$ 0
Defaulted, number of loans/leases | loan	0	0	0
Defaulted, recorded investment	$ 0	$ 0	$ 0
Originated | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	3	10	10
Recorded Investment, At Modification	$ 6,794	$ 1,775	$ 7,861
Recorded Investment, At end of period	5,457	1,706	3,911
Specific Allowance for Loan and Lease Losses	2,455	733	191
Nonaccrual Loans and Leases	$ 1,912	$ 1,706	$ 2,189
Defaulted, number of loans/leases | loan	1	2	2
Defaulted, recorded investment	$ 1,912	$ 1,075	$ 1,361
Originated | Equipment financing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	7	14	16
Recorded Investment, At Modification	$ 2,774	$ 2,510	$ 2,687
Recorded Investment, At end of period	2,266	2,556	2,901
Specific Allowance for Loan and Lease Losses	0	37	137
Nonaccrual Loans and Leases	$ 392	$ 1,351	$ 1,440
Defaulted, number of loans/leases | loan	2	0	1
Defaulted, recorded investment	$ 365	$ 0	$ 188
Originated | Residential mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	3	2
Recorded Investment, At Modification	$ 868	$ 550
Recorded Investment, At end of period	866	550
Specific Allowance for Loan and Lease Losses	0	12
Nonaccrual Loans and Leases	$ 96	$ 341
Defaulted, number of loans/leases | loan	0	1
Defaulted, recorded investment	$ 0	$ 341
Originated | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	3	1
Recorded Investment, At Modification	$ 453	$ 86
Recorded Investment, At end of period	453	83
Specific Allowance for Loan and Lease Losses	0	0
Nonaccrual Loans and Leases	$ 0	$ 0
Defaulted, number of loans/leases | loan	0	0
Defaulted, recorded investment	$ 0	$ 0
Acquired
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	3	2
Recorded Investment, At Modification	$ 5,300	$ 249
Recorded Investment, At end of period	3,370	245
Specific Allowance for Loan and Lease Losses	0	0
Nonaccrual Loans and Leases	$ 133	$ 245
Defaulted, number of loans/leases | loan	0	0
Defaulted, recorded investment	$ 0	$ 0
Acquired | Construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	1
Recorded Investment, At Modification	$ 4,869
Recorded Investment, At end of period	2,942
Specific Allowance for Loan and Lease Losses	0
Nonaccrual Loans and Leases	$ 0
Defaulted, number of loans/leases | loan	0
Defaulted, recorded investment	$ 0
Acquired | Residential mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	1
Recorded Investment, At Modification	$ 297
Recorded Investment, At end of period	295
Specific Allowance for Loan and Lease Losses	0
Nonaccrual Loans and Leases	$ 0
Defaulted, number of loans/leases | loan	0
Defaulted, recorded investment	$ 0
Acquired | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans/ Leases | loan	1	2
Recorded Investment, At Modification	$ 134	$ 249
Recorded Investment, At end of period	133	245
Specific Allowance for Loan and Lease Losses	0	0
Nonaccrual Loans and Leases	$ 133	$ 245
Defaulted, number of loans/leases | loan	0	0
Defaulted, recorded investment	$ 0	$ 0

Premises and Equipment (Summary

Premises and Equipment (Summary of Premises and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Premises and Equipment
Premises and Equipment, gross amount	$ 151,113	$ 146,522
Accumulated depreciation and amortization	76,763	70,140
Total premises and equipment	74,350	76,382
Land
Premises and Equipment
Premises and Equipment, gross amount	12,320	12,300
Fine art
Premises and Equipment
Premises and Equipment, gross amount	545	533
Computer equipment
Premises and Equipment
Premises and Equipment, gross amount	$ 11,886	$ 10,488
Estimated useful life	3 years	3 years
Vehicles
Premises and Equipment
Premises and Equipment, gross amount	$ 135	$ 126
Core processing system and software
Premises and Equipment
Premises and Equipment, gross amount	20,748	20,466
Furniture, fixtures and equipment
Premises and Equipment
Premises and Equipment, gross amount	15,393	14,696
Office building and improvements
Premises and Equipment
Premises and Equipment, gross amount	$ 90,086	$ 87,913
Minimum | Vehicles
Premises and Equipment
Estimated useful life	3 years	3 years
Minimum | Core processing system and software
Premises and Equipment
Estimated useful life	3 years	3 years
Minimum | Furniture, fixtures and equipment
Premises and Equipment
Estimated useful life	5 years	5 years
Minimum | Office building and improvements
Premises and Equipment
Estimated useful life	10 years	10 years
Maximum | Vehicles
Premises and Equipment
Estimated useful life	5 years	5 years
Maximum | Core processing system and software
Premises and Equipment
Estimated useful life	7 years 6 months	7 years 6 months
Maximum | Furniture, fixtures and equipment
Premises and Equipment
Estimated useful life	25 years	25 years
Maximum | Office building and improvements
Premises and Equipment
Estimated useful life	40 years	40 years

Premises and Equipment (Narrati

Premises and Equipment (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 7	$ 7.5	$ 7.4

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Rollforward of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Balance at beginning of year	$ 160,427	$ 137,890	$ 137,890
Additions	0	22,537	0
Balance at end of year	$ 160,427	$ 160,427	$ 137,890

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets (Summary of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other intangibe assets:
Gross amount	$ 41,904	$ 41,904
Accumulated amortization	37,481	35,818
Carrying Amount	4,423	6,086
Core deposits
Other intangibe assets:
Gross amount	38,294	38,294
Accumulated amortization	34,960	33,297
Carrying Amount	3,334	4,997
Trade name
Other intangibe assets:
Gross amount	1,600	1,600
Accumulated amortization	511	511
Carrying Amount	1,089	1,089
Trust relationship
Other intangibe assets:
Gross amount	1,568	1,568
Accumulated amortization	1,568	1,568
Carrying Amount	0	0
Other intangible
Other intangibe assets:
Gross amount	442	442
Accumulated amortization	442	442
Carrying Amount	$ 0	$ 0

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2013
Indefinite-lived Intangible Assets [Line Items]
Impairment losses	$ 0	$ 0	$ 0
Trade name
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets				$ 1,100,000
Core deposits
Indefinite-lived Intangible Assets [Line Items]
Weighted-average amortization period	7 years 14 days

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets (Future Amortization Expense) (Details) $ in Thousands	Dec. 31, 2019USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2020	$ 1,297
2021	850
2022	494
2023	263
2024	153
Thereafter	277
Total	$ 3,334

Other Assets (Narrative) (Detai

Other Assets (Narrative) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019USD ($)project	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)policyproject	Dec. 31, 2018USD ($)policy	Dec. 31, 2017USD ($)policy	Dec. 31, 2014USD ($)	Jan. 01, 2015USD ($)
Business Acquisition [Line Items]
Number of policies owned | policy									9	9	9
Net income attributable to Brookline Bancorp, Inc.	$ 22,183	$ 22,596	$ 20,471	$ 22,467	$ 21,138	$ 22,460	$ 20,831	$ 18,633	$ 87,717	$ 83,062	$ 50,518
Affordable housing project
Business Acquisition [Line Items]
Number of investments | project	17								17
Maximum percentage of outstanding equity interest that can be invested by the entity in any single project									50.00%
Other non-interest income
Business Acquisition [Line Items]
Tax exempt BOLI income									$ 1,000	$ 1,000	$ 1,000
BankRI
Business Acquisition [Line Items]
Number of policies owned | policy									7	7
Net cash surrender value	$ 41,000				39,900				$ 41,000	$ 39,900
First Ipswich
Business Acquisition [Line Items]
Number of policies owned | policy									2	2
Net cash surrender value	$ 800				$ 800				$ 800	$ 800
ASU 2014-01
Business Acquisition [Line Items]
Net income attributable to Brookline Bancorp, Inc.												$ 500
Retained earnings													$ 1,100

Other Assets (Additional Inform

Other Assets (Additional Information on Investments in Affordable Housing Projects) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments in Affordable Housing Projects [Abstract]
Investments in affordable housing projects included in other assets	$ 167,431	$ 103,214
Unfunded commitments related to affordable housing projects included in other liabilities	1,900	1,900
Investment amortization included in provision for income taxes	2,097	1,916	$ 1,844
Amount recognized as income tax benefit	540	585	$ 623
Affordable housing project
Investments in Affordable Housing Projects [Abstract]
Investments in affordable housing projects included in other assets	29,939	10,895
Unfunded commitments related to affordable housing projects included in other liabilities	20,286	1,115
Investment in affordable housing tax credits	2,042	1,885
Investment in affordable housing tax benefits	$ 540	$ 585

Deposits (Summary of Deposits)

Deposits (Summary of Deposits) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Banking and Thrift [Abstract]
Demand checking accounts	$ 1,141,578	$ 1,033,551
NOW accounts	371,380	336,317
Savings accounts	613,467	619,961
Money market accounts	1,682,005	1,675,050
Total core deposit accounts	3,808,430	3,664,879
Certificate of deposit accounts maturing:
Within six months	730,512	475,303
After six months but within 1 year	650,461	562,018
After 1 year but within 2 years	495,509	538,435
After 2 years but within 3 years	56,508	95,806
After 3 years but within 4 years	58,492	46,027
After 4 years but within 5 years	29,759	71,556
After 5 Years	401	20
Total certificate of deposit accounts	2,021,642	1,789,165
Total deposits	$ 5,830,072	$ 5,454,044
Weighted Average Rate of Demand checking accounts
Demand checking accounts (as a percent)	0.00%	0.00%
NOW accounts (as a percent)	0.11%	0.10%
Savings accounts (as a percent)	0.46%	0.32%
Money market savings accounts (as a percent)	1.15%	1.18%
Total transaction deposit accounts (as a percent)	0.59%	0.60%
Weighted Average Rate of Certificate of deposit accounts maturing:
Within six months (as a percent)	2.24%	1.20%
After six months but within 1 year (as a percent)	2.24%	1.40%
After 1 year but within 2 years (as a percent)	2.26%	1.85%
After 2 years but within 3 years (as a percent)	2.19%	2.16%
After 3 years but within 4 years (as a percent)	2.64%	1.73%
After 4 years but within 5 years (as a percent)	2.58%	2.57%
After 5 years (as a percent)	2.19%	1.98%
Total certificate of deposit accounts (as a percent)	2.26%	1.58%
Total of weighted average rate of deposits (as a percent)	1.17%	0.92%

Deposits (Interest Expense) (De

Deposits (Interest Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest-bearing deposits:
NOW accounts	$ 436	$ 283	$ 225
Savings accounts	2,900	1,804	1,297
Money market accounts	21,206	15,369	8,863
Certificate of deposit accounts	45,073	24,522	12,903
Total interest-bearing deposits	$ 69,615	$ 41,978	$ 23,288

Deposits (Narrative) (Details)

Deposits (Narrative) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Banking and Thrift [Abstract]
Threshold for disclosure of time deposit issued amounts	$ 250,000	$ 250,000
Time Deposits, $100,000 or More	557,500,000	480,800,000
Related party deposits	70,400,000	59,800,000
Deposits pledged as collateral	$ 184,000,000	$ 211,500,000

Borrowed Funds (Components and

Borrowed Funds (Components and Interest Expenses of Borrowed Funds) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total borrowed funds	$ 902,749	$ 920,542
Total interest expense on borrowed funds	24,711	24,216	$ 16,581
Advances from the FHLBB
Debt Instrument [Line Items]
Total borrowed funds	758,469	784,375
Total interest expense on borrowed funds	18,701	18,650	11,330
Subordinated debentures and notes
Debt Instrument [Line Items]
Total borrowed funds	83,591	83,433
Total interest expense on borrowed funds	5,206	5,181	5,081
Other borrowed funds
Debt Instrument [Line Items]
Total borrowed funds	60,689	52,734
Total interest expense on borrowed funds	$ 804	$ 385	$ 170

Borrowed Funds (Narrative) (Det

Borrowed Funds (Narrative) (Details) - USD ($)	Sep. 15, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Securities available-for-sale and loans pledged as collateral		$ 2,500,000,000	$ 2,400,000,000
Total available borrowing capacity from Federal Home Loan Bank		2,200,000,000
Qualifying collateral available for Federal Home Loan Bank borrowings		3,500,000,000
Outstanding at end of year		902,749,000	920,542,000
Accretion adjustment		(1,810,000)	(2,200,000)	$ (2,042,000)
Repurchase agreements
Debt Instrument [Line Items]
Decrease in agreement amount		(10,000,000)
Outstanding at end of year		42,700,000	52,700,000
Committed line of credit | Line of credit
Debt Instrument [Line Items]
Borrowing capacity		12,000,000
Uncommitted lines of credit | Line of credit
Debt Instrument [Line Items]
Borrowing capacity		475,000,000
Outstanding balance		18,000,000	0
Subordinated debenture maturing September 15, 2029
Debt Instrument [Line Items]
Outstanding at end of year		$ 74,026,000	73,926,000
Subordinated debenture maturing September 15, 2029 | Interest rate period 1
Debt Instrument [Line Items]
Fixed interest rate		6.00%
Subordinated debenture maturing September 15, 2029 | Interest rate period 2 | LIBOR
Debt Instrument [Line Items]
Variable interest rate spread (as a percent)		3.315%
Subordinated debenture maturing September 15, 2029 | Subordinated debentures and notes
Debt Instrument [Line Items]
Principal amount	$ 75,000,000
Accretion adjustment		$ 400,000	500,000
Capitalized financing costs		$ 1,000,000	$ 1,100,000
Subordinated debenture maturing September 15, 2029 | Subordinated debentures and notes | Interest rate period 1
Debt Instrument [Line Items]
Fixed interest rate	6.00%
Subordinated debenture maturing September 15, 2029 | Subordinated debentures and notes | Interest rate period 2 | LIBOR
Debt Instrument [Line Items]
Variable interest rate spread (as a percent)	3.315%

Borrowed Funds (FHLBB Advances)

Borrowed Funds (FHLBB Advances) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amount
Within 1 year	$ 599,262	$ 603,590
Over 1 year to 2 years	139,762	160,073
Over 2 years to 3 years	3,210	580
Over 3 years to 4 years	0	3,214
Over 4 years to 5 years	4,025	0
Over 5 years	12,210	16,918
Total	758,469	784,375
Callable Amount
Within 1 year	0	0
Over 1 year to 2 years	0	0
Over 2 years to 3 years	0	0
Over 3 years to 4 years	0	0
Over 4 years to 5 years	0	0
Over 5 years	0	0
Total	$ 0	$ 0
Weighted Average Rate
Within 1 year (as a percent)	2.27%	2.19%
Over 1 year to 2 years (as a percent)	2.12%	2.64%
Over 2 years to 3 years (as a percent)	0.01%	3.07%
Over 3 years to 4 years (as a percent)	0.00%	0.03%
Over 4 years to 5 years (as a percent)	3.91%	0.00%
Over 5 years (as a percent)	3.28%	3.45%
Weighted average interest rate of total advances from the FHLB (as a percent)	2.26%	2.30%

Borrowed Funds (Other Borrowed

Borrowed Funds (Other Borrowed Funds) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Outstanding at end of year	$ 902,749	$ 920,542
Other borrowed funds
Debt Instrument [Line Items]
Outstanding at end of year	60,689	52,734
Average outstanding for the year	79,276	46,079
Maximum outstanding at any month-end	$ 122,776	$ 55,144
Weighted average rate at end of year	0.60%	0.16%
Weighted average rate paid for the year	1.01%	0.83%

Borrowed Funds (Summary of Subo

Borrowed Funds (Summary of Subordinated Debentures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total borrowed funds	$ 902,749	$ 920,542
Subordinated debenture maturing June 26, 2033
Debt Instrument [Line Items]
Total borrowed funds	4,826	4,803
Subordinated debenture maturing March 17, 2034
Debt Instrument [Line Items]
Total borrowed funds	4,739	4,704
Subordinated debenture maturing September 15, 2029
Debt Instrument [Line Items]
Total borrowed funds	74,026	73,926
Subordinated Debentures Maturing June 26, 2033, March 17, 2034 and September 15, 2029
Debt Instrument [Line Items]
Total borrowed funds	$ 83,591	$ 83,433
LIBOR | Subordinated debenture maturing June 26, 2033
Debt Instrument [Line Items]
Variable interest rate spread (as a percent)	3.10%
LIBOR | Subordinated debenture maturing March 17, 2034
Debt Instrument [Line Items]
Variable interest rate spread (as a percent)	2.79%

Commitments and Contingencies_2

Commitments and Contingencies (Financial Instruments with Off-Balance Sheet Risk) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Loan commitments
Unadvanced portion of loans and leases	$ 808,681	$ 707,997
Unused lines of credit:
Home equity	528,251	487,476
Other consumer	25,374	50,404
Other commercial	380	347
Unused letters of credit:
Financial standby letters of credit	10,166	11,491
Performance standby letters of credit	4,652	3,075
Commercial and similar letters of credit	3,823	4,573
Commercial real estate
Loan commitments
Commitments to originate loans and leases	50,034	76,642
Commercial
Loan commitments
Commitments to originate loans and leases	78,058	75,713
Residential mortgage
Loan commitments
Commitments to originate loans and leases	25,998	16,363
Receive fixed, pay variable
Unused letters of credit:
Derivatives	1,101,193	714,500
Pay fixed, receive variable
Unused letters of credit:
Derivatives	1,101,193	714,500
Risk participation-out agreements
Unused letters of credit:
Derivatives	235,693	100,531
Risk participation-in agreements
Unused letters of credit:
Derivatives	55,281	35,838
Foreign exchange contracts | Buys foreign currency, sells U.S. currency
Unused letters of credit:
Derivatives	1,125	6,573
Foreign exchange contracts | Sells foreign currency, buys U.S. currency
Unused letters of credit:
Derivatives	$ 1,230	$ 6,582

Commitments and Contingencies_3

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Unfunded credit commitments liability	$ 1.9	$ 1.9
Fair value of interest rate swap assets	60.6	22.5
Fair value of interest rate swap liabilities	59.7	22.2
Lessee, Lease, Description [Line Items]
Total operating rental expense	6.2
Total rental expense		5.8	$ 5.5
Rental income	$ 0.4	$ 0.4	$ 0.4
Minimum
Lessee, Lease, Description [Line Items]
Term of operating lease	3 years
Maximum
Lessee, Lease, Description [Line Items]
Term of operating lease	25 years

Commitments and Contingencies_4

Commitments and Contingencies (Lease Costs, Cash Flows and Balance Sheet Supplemental Information) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 6,461
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	6,515
Right-of-use assets obtained in exchange for new lease obligations:
Operating leases	66
Supplemental balance sheet information related to operating leases was as follows:
Operating lease right-of-use assets	24,876	$ 24,876
Operating lease liabilities	$ 24,876	$ 24,876
Weighted Average Remaining Lease Term
Operating leases	7 years 5 months 19 days
Weighted Average Discount Rate
Operating leases	3.20%

Commitments and Contingencies_5

Commitments and Contingencies (Maturities of Operating Leases) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Operating Leases, After Adoption of 842
2020	$ 5,886
2021	5,267
2022	4,577
2023	3,672
2024	2,305
Thereafter	6,163
Total	27,870
Less imputed interest	(2,994)
Operating lease liabilities	$ 24,876	$ 24,876

Earnings per Share (EPS) (Detai

Earnings per Share (EPS) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income (in usd)									$ 87,717	$ 83,062	$ 50,518
Weighted average shares outstanding	79,682,724	79,700,403	79,669,922	79,658,583	80,258,489	80,315,050	80,184,977	77,879,593	79,679,781	79,669,668	74,459,508
Effect of dilutive securities									177,140	239,583	351,900
Adjusted weighted average shares outstanding	79,845,447	79,883,510	79,886,292	79,843,578	80,407,558	80,515,467	80,505,614	78,167,800	79,856,921	79,909,251	74,811,408
Basic EPS (in dollars per share)	$ 0.28	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.24	$ 1.10	$ 1.04	$ 0.68
Diluted EPS (in dollars per share)	$ 0.28	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.24	$ 1.10	$ 1.04	$ 0.68

Comprehensive Income_(Loss) (Ch

Comprehensive Income/(Loss) (Changes in AOCI) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in accumulated other comprehensive (loss) income by component, net of tax
Balance beginning of period	$ 910,619	$ 812,583	$ 702,749
Other comprehensive income (loss)	11,743	(3,510)	(1,069)
Balance end of period	945,606	910,619	812,583
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive (loss) income by component, net of tax
Balance beginning of period	(9,460)	(5,950)	(3,818)
Other comprehensive income (loss)	11,743	(3,510)	(1,069)
Reclassification due to the adoption of ASU No. 2018-02		0	(1,063)
Balance end of period	2,283	(9,460)	(5,950)
Investment Securities Available-for-Sale
Changes in accumulated other comprehensive (loss) income by component, net of tax
Balance beginning of period	(9,712)	(6,113)	(4,213)
Other comprehensive income (loss)	11,911	(3,599)	(817)
Reclassification due to the adoption of ASU No. 2018-02		0	(1,083)
Balance end of period	2,199	(9,712)	(6,113)
Postretirement Benefits
Changes in accumulated other comprehensive (loss) income by component, net of tax
Balance beginning of period	252	163	395
Other comprehensive income (loss)	(168)	89	(252)
Reclassification due to the adoption of ASU No. 2018-02		0	20
Balance end of period	$ 84	$ 252	$ 163

Derivatives and Hedging Activ_3

Derivatives and Hedging Activities (Summary of Derivative Positions) (Details)	12 Months Ended
	Dec. 31, 2019USD ($)derivative	Dec. 31, 2018USD ($)derivative
Loss Recognized in Income on Derivatives
Gain (loss) recognized in income	$ 679,000	$ 206,000
Estimated net credit risk exposure	0	0
Collateral posted	86,500,000	5,900,000
Receive fixed, pay variable
Derivatives and Hedging Activities
Total	$ 1,101,193,000	$ 714,500,000
Receive fixed, pay variable | Derivatives not designed as hedging instruments
Derivatives and Hedging Activities
Number of Positions | derivative	119,000	86,000
Notional Amount Maturing, Less than 1 year	$ 24,777,000	$ 1,931,000
Notional Amount Maturing, Less than 2 years	0	26,419,000
Notional Amount Maturing, Less than 3 years	31,131,000	0
Notional Amount Maturing, Less than 4 years	16,794,000	31,762,000
Notional Amount Maturing, Thereafter	1,028,491,000	654,388,000
Total	1,101,193,000	714,500,000
Fair Value	58,102,000	6,081,000
Pay fixed, receive variable
Derivatives and Hedging Activities
Total	$ 1,101,193,000	$ 714,500,000
Pay fixed, receive variable | Derivatives not designed as hedging instruments
Derivatives and Hedging Activities
Number of Positions | derivative	119,000	86,000
Notional Amount Maturing, Less than 1 year	$ 24,777,000	$ 1,931,000
Notional Amount Maturing, Less than 2 years	0	26,419,000
Notional Amount Maturing, Less than 3 years	31,131,000	0
Notional Amount Maturing, Less than 4 years	16,794,000	31,762,000
Notional Amount Maturing, Thereafter	1,028,491,000	654,388,000
Total	1,101,193,000	714,500,000
Fair Value	58,102,000	6,081,000
Risk participation-out agreements
Derivatives and Hedging Activities
Total	235,693,000	100,531,000
Loss Recognized in Income on Derivatives
Gain (loss) recognized in income	$ 686,000	$ 205,000
Risk participation-out agreements | Derivatives not designed as hedging instruments
Derivatives and Hedging Activities
Number of Positions | derivative	40,000	26,000
Notional Amount Maturing, Less than 1 year	$ 13,967,000	$ 0
Notional Amount Maturing, Less than 2 years	0	14,892,000
Notional Amount Maturing, Less than 3 years	0	0
Notional Amount Maturing, Less than 4 years	7,143,000	0
Notional Amount Maturing, Thereafter	214,583,000	85,639,000
Total	235,693,000	100,531,000
Fair Value	1,229,000	344,000
Risk participation-in agreements
Derivatives and Hedging Activities
Total	$ 55,281,000	$ 35,838,000
Risk participation-in agreements | Derivatives not designed as hedging instruments
Derivatives and Hedging Activities
Number of Positions | derivative	7,000	5,000
Notional Amount Maturing, Less than 1 year	$ 0	$ 0
Notional Amount Maturing, Less than 2 years	0	0
Notional Amount Maturing, Less than 3 years	0	0
Notional Amount Maturing, Less than 4 years	19,000,000	0
Notional Amount Maturing, Thereafter	36,281,000	35,838,000
Total	55,281,000	35,838,000
Fair Value	283,000	84,000
Foreign exchange contracts
Loss Recognized in Income on Derivatives
Gain (loss) recognized in income	(7,000)	1,000
Buys foreign currency, sells U.S. currency | Foreign exchange contracts
Derivatives and Hedging Activities
Total	$ 1,125,000	$ 6,573,000
Buys foreign currency, sells U.S. currency | Foreign exchange contracts | Derivatives not designed as hedging instruments
Derivatives and Hedging Activities
Number of Positions | derivative	16,000	22,000
Notional Amount Maturing, Less than 1 year	$ 1,125,000	$ 6,573,000
Notional Amount Maturing, Less than 2 years	0	0
Notional Amount Maturing, Less than 3 years	0	0
Notional Amount Maturing, Less than 4 years	0	0
Notional Amount Maturing, Thereafter	0	0
Total	1,125,000	6,573,000
Fair Value	54,000	123,000
Sells foreign currency, buys U.S. currency | Foreign exchange contracts
Derivatives and Hedging Activities
Total	$ 1,230,000	$ 6,582,000
Sells foreign currency, buys U.S. currency | Foreign exchange contracts | Derivatives not designed as hedging instruments
Derivatives and Hedging Activities
Number of Positions | derivative	18,000	37,000
Notional Amount Maturing, Less than 1 year	$ 1,230,000	$ 6,582,000
Notional Amount Maturing, Less than 2 years	0	0
Notional Amount Maturing, Less than 3 years	0	0
Notional Amount Maturing, Less than 4 years	0	0
Notional Amount Maturing, Thereafter	0	0
Total	1,230,000	6,582,000
Fair Value	$ 53,000	$ 131,000

Derivatives and Hedging Activ_4

Derivatives and Hedging Activities (Amounts Subject to Master Netting Agreement) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Asset derivatives
Assets, Gross Amounts Recognized	$ 60,648	$ 22,488
Assets, Gross Amounts Offset in the Statement of Financial Position	0	0
Assets, Net Amounts Presented in the Statement of Financial Position	60,648	22,488
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	0	0
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	11,900	50
Assets, Net Amount	48,748	22,438
Liability derivatives
Liabilities, Gross Amounts Recognized	59,701	22,220
Liabilities, Gross Amounts Offset in the Statement of Financial Position	0	0
Liabilities, Net Amounts Presented in the Statement of Financial Position	59,701	22,220
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	86,521	5,877
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	0	0
Liabilities, Net Amount	(26,820)	16,343
Loan level derivatives
Asset derivatives
Assets, Gross Amounts Recognized	59,365	22,013
Assets, Gross Amounts Offset in the Statement of Financial Position	0	0
Assets, Net Amounts Presented in the Statement of Financial Position	59,365	22,013
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	0	0
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	11,900	50
Assets, Net Amount	47,465	21,963
Liability derivatives
Liabilities, Gross Amounts Recognized	59,365	22,013
Liabilities, Gross Amounts Offset in the Statement of Financial Position	0	0
Liabilities, Net Amounts Presented in the Statement of Financial Position	59,365	22,013
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	86,521	5,877
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	0	0
Liabilities, Net Amount	(27,156)	16,136
Risk participation-out agreements
Asset derivatives
Assets, Gross Amounts Recognized	1,229	344
Assets, Gross Amounts Offset in the Statement of Financial Position	0	0
Assets, Net Amounts Presented in the Statement of Financial Position	1,229	344
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	0	0
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	0	0
Assets, Net Amount	1,229	344
Risk participation-in agreements
Liability derivatives
Liabilities, Gross Amounts Recognized	283	84
Liabilities, Gross Amounts Offset in the Statement of Financial Position	0	0
Liabilities, Net Amounts Presented in the Statement of Financial Position	283	84
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	0	0
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	0	0
Liabilities, Net Amount	283	84
Foreign exchange contracts
Asset derivatives
Assets, Gross Amounts Recognized	54	131
Assets, Gross Amounts Offset in the Statement of Financial Position	0	0
Assets, Net Amounts Presented in the Statement of Financial Position	54	131
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	0	0
Assets, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	0	0
Assets, Net Amount	54	131
Liability derivatives
Liabilities, Gross Amounts Recognized	53	123
Liabilities, Gross Amounts Offset in the Statement of Financial Position	0	0
Liabilities, Net Amounts Presented in the Statement of Financial Position	53	123
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments Pledged	0	0
Liabilities, Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Pledged	0	0
Liabilities, Net Amount	$ 53	$ 123

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current provision:
Federal									$ 21,706	$ 23,949	$ 27,825
State									6,565	7,693	5,013
Total current provision									28,271	31,642	32,838
Deferred provision (benefit):
Federal									701	(4,323)	10,209
State									(703)	(1,130)	589
Total deferred provision (benefit)									(2)	(5,453)	10,798
Total provision for income taxes	$ 7,087	$ 7,507	$ 6,780	$ 6,895	$ 7,055	$ 6,140	$ 7,342	$ 5,652	$ 28,269	$ 26,189	$ 43,636

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation Allowance [Line Items]
Effective income tax rate (as a percent)	24.40%	23.20%	44.90%
Increase in expected income tax expense at statutory federal tax rate	$ 700
Income attributable to noncontrolling interest in subsidiary	11	$ 933	$ 870
Tax Act Adjustment	0	$ (707)	$ 8,965
Net operating loss carryforwards for U.S. federal income tax purposes	900
Reserve for loan losses	$ 1,800
Percentage of the amount the used reserve for loan losses would be subject to taxation, if, the reserve is used for purposes other than to absorb the losses for which it was established	150.00%
Amount of liability that would result if 100% of the reserve were recaptured on which no provision has been made	$ 500
Reserve for loan losses recaptured (as a percent)	100.00%
Deferred Tax Assets
Valuation Allowance [Line Items]
Tax Act Adjustment	$ 8,600
Affordable housing project
Valuation Allowance [Line Items]
Tax Act Adjustment	300
First Commons Bank
Valuation Allowance [Line Items]
Net operating loss carryforwards for U.S. federal income tax purposes	$ 700

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of Effective Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory U.S federal income tax rate (as a percent)									21.00%	21.00%	35.00%
Reconciliation of income tax expense
Expected income tax expense at statutory federal tax rate									$ 24,366	$ 23,675	$ 34,039
State taxes, net of federal income tax benefit									4,837	5,184	3,641
Bank-owned life insurance									(216)	(218)	(364)
Tax-exempt interest income									(435)	(487)	(873)
Income attributable to noncontrolling interest in subsidiary									(11)	(933)	(870)
Merger and acquisition expense									0	32	138
Tax Act Adjustment									0	(707)	8,965
Investments in affordable housing projects									(369)	(358)	(653)
Other, net									97	1	(387)
Total provision for income taxes	$ 7,087	$ 7,507	$ 6,780	$ 6,895	$ 7,055	$ 6,140	$ 7,342	$ 5,652	$ 28,269	$ 26,189	$ 43,636
Effective income tax rate (as a percent)									24.40%	23.20%	44.90%

Income Taxes (Components of Def

Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for loan and lease losses	$ 16,294	$ 15,936
Right-of-use asset - operating leases	6,450
Deferred compensation	4,748	4,692
Identified intangible assets and goodwill	4,319	0
Supplemental Executive Retirement Plans	3,023	2,846
Unrealized loss on investment securities available-for-sale	0	2,737
Net operating loss carryforwards	187	976
Postretirement benefits	458	391
Nonaccrual interest	557	482
Accrued expense	0	372
Restricted stock and stock option plans	751	497
Employee stock ownership plan	83	106
Other	733	331
Total gross deferred tax assets	37,603	29,366
Deferred tax liabilities:
Operating leases - liability	6,450
Identified intangible assets and goodwill	0	2,428
Deferred loan origination costs, net	3,785	3,537
Depreciation	420	789
Unrealized gain on investment securities available-for-sale	622	0
Prepaid expense	110	116
Accrued Expense	122	0
Acquisition fair value adjustments	1,077	1,001
Total gross deferred tax liabilities	12,586	7,871
Net deferred tax asset	$ 25,017	$ 21,495

Stockholders' Equity (Narrative

Stockholders' Equity (Narrative) (Details) - USD ($)	May 02, 2017	Apr. 27, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016	Dec. 04, 2019	Jan. 30, 2019	Dec. 05, 2018	Dec. 31, 2017	Feb. 04, 2016
Equity [Abstract]
Authorized serial preferred stock (in shares)			50,000,000
Serial preferred stock, par value (in dollars per share)			$ 0.01
Preferred stock issued (in shares)			0
Stock repurchase program, authorized amount						$ 10,000,000	$ 10,000,000	$ 10,000,000		$ 10,000,000
Number of shares repurchased (in shares)			103,758	725,583	0
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in dollars per share)			$ 0.01	$ 0.01
Proceeds from the issuance of common stock	$ 82,000,000
Liquidation account, total			$ 11,900,000	$ 13,000,000					$ 15,100,000
Public stock offering
Subsidiary, Sale of Stock [Line Items]
Shares in offering (in shares)		5,175,000
Common stock, par value (in dollars per share)		$ 0.01
Sale of stock price (in usd per share)		$ 14.50
Underwriters option
Subsidiary, Sale of Stock [Line Items]
Shares in offering (in shares)	5,951,250	776,250
Sale of stock price (in usd per share)	$ 14.50

Regulatory Capital Requiremen_3

Regulatory Capital Requirements (Narrative) (Details) - Brookline Bank	Dec. 31, 2019	Dec. 31, 2018
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total (as a percent)	10.00%	10.00%
Tier 1 (as a percent)	8.00%	8.00%
Common equity Tier 1 capital ratio, Minimum Required to Be Considered Well-Capitalized, Ratio (as a percent)	6.50%	6.50%
Tier 1 leverage capital ratio (as a percent)	5.00%	5.00%

Regulatory Capital Requiremen_4

Regulatory Capital Requirements (Summary of Regulatory Capital Requirements) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Bank actual capital amount
Common equity Tier 1 capital ratio, Actual, Amount	$ 780,962	$ 745,103
Tier 1 leverage capital	790,527	765,089
Risk-based capital:
Tier 1	790,527	765,089
Total risk-based capital	$ 927,515	$ 899,563
Bank actual capital ratio
Common equity Tier 1 capital ratio, Actual, Ratio (as a percent)	11.44%	11.94%
Tier 1 leverage capital ratio (as a percent)	10.28%	10.58%
Risk-based capital:
Tier 1 (as a percent)	11.58%	12.26%
Total (as a percent)	13.59%	14.42%
Minimum capital adequacy amount
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Amount	$ 307,197	$ 280,818
Tier 1 leverage capital	307,598	289,259
Risk-based capital:
Tier 1	409,599	374,432
Total	$ 545,999	$ 499,064
Minimum capital adequacy ratio
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Ratio (as a percent)	4.50%	4.50%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	6.00%	6.00%
Total (as a percent)	8.00%	8.00%
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio	$ 477,861	$ 436,828
Tier 1 leverage capital ratio	307,598	289,259
Risk-based capital:
Tier 1 risk-based capital ratio	580,266	530,445
Total risk-based capital ratio	$ 716,623	$ 655,022
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio (as a percent)	7.00%	7.00%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	8.50%	8.50%
Total (as a percent)	10.50%	10.50%
Brookline Bank
Bank actual capital amount
Common equity Tier 1 capital ratio, Actual, Amount	$ 513,311	$ 495,798
Tier 1 leverage capital	513,311	506,277
Risk-based capital:
Tier 1	513,311	506,277
Total risk-based capital	$ 555,474	$ 545,533
Bank actual capital ratio
Common equity Tier 1 capital ratio, Actual, Ratio (as a percent)	11.44%	12.06%
Tier 1 leverage capital ratio (as a percent)	10.42%	11.02%
Risk-based capital:
Tier 1 (as a percent)	11.44%	12.32%
Total (as a percent)	12.38%	13.27%
Minimum capital adequacy amount
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Amount	$ 201,914	$ 184,999
Tier 1 leverage capital	197,048	183,767
Risk-based capital:
Tier 1	269,219	246,563
Total	$ 358,949	$ 328,882
Minimum capital adequacy ratio
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Ratio (as a percent)	4.50%	4.50%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	6.00%	6.00%
Total (as a percent)	8.00%	8.00%
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio	$ 314,089	$ 287,777
Tier 1 leverage capital ratio	197,048	183,767
Risk-based capital:
Tier 1 risk-based capital ratio	381,394	349,298
Total risk-based capital ratio	$ 471,121	$ 431,658
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio (as a percent)	7.00%	7.00%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	8.50%	8.50%
Total (as a percent)	10.50%	10.50%
Classified as well capitalized
Common equity Tier 1 capital ratio, Minimum Required to Be Considered Well-Capitalized, Amount	$ 291,654	$ 267,221
Tier 1 leverage capital	246,310	229,708
Risk-based capital:
Tier 1	358,959	328,751
Total	$ 448,687	$ 411,102
Classified as well capitalized ratio
Common equity Tier 1 capital ratio, Minimum Required to Be Considered Well-Capitalized, Ratio (as a percent)	6.50%	6.50%
Tier 1 leverage capital ratio (as a percent)	5.00%	5.00%
Risk-based capital:
Tier 1 (as a percent)	8.00%	8.00%
Total (as a percent)	10.00%	10.00%
BankRI
Bank actual capital amount
Common equity Tier 1 capital ratio, Actual, Amount	$ 240,362	$ 209,670
Tier 1 leverage capital	240,362	209,670
Risk-based capital:
Tier 1	240,362	209,670
Total risk-based capital	$ 258,719	$ 227,674
Bank actual capital ratio
Common equity Tier 1 capital ratio, Actual, Ratio (as a percent)	11.75%	11.37%
Tier 1 leverage capital ratio (as a percent)	9.97%	9.35%
Risk-based capital:
Tier 1 (as a percent)	11.75%	11.37%
Total (as a percent)	12.65%	12.35%
Minimum capital adequacy amount
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Amount	$ 92,054	$ 82,983
Tier 1 leverage capital	96,434	89,698
Risk-based capital:
Tier 1	122,738	110,644
Total	$ 163,617	$ 147,481
Minimum capital adequacy ratio
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Ratio (as a percent)	4.50%	4.50%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	6.00%	6.00%
Total (as a percent)	8.00%	8.00%
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio	$ 143,194	$ 129,084
Tier 1 leverage capital ratio	96,434	89,698
Risk-based capital:
Tier 1 risk-based capital ratio	173,879	156,745
Total risk-based capital ratio	$ 214,747	$ 193,569
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio (as a percent)	7.00%	7.00%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	8.50%	8.50%
Total (as a percent)	10.50%	10.50%
Classified as well capitalized
Common equity Tier 1 capital ratio, Minimum Required to Be Considered Well-Capitalized, Amount	$ 132,966	$ 119,864
Tier 1 leverage capital	120,543	112,123
Risk-based capital:
Tier 1	163,651	147,525
Total	$ 204,521	$ 184,351
Classified as well capitalized ratio
Common equity Tier 1 capital ratio, Minimum Required to Be Considered Well-Capitalized, Ratio (as a percent)	6.50%	6.50%
Tier 1 leverage capital ratio (as a percent)	5.00%	5.00%
Risk-based capital:
Tier 1 (as a percent)	8.00%	8.00%
Total (as a percent)	10.00%	10.00%
First Ipswich
Bank actual capital amount
Common equity Tier 1 capital ratio, Actual, Amount	$ 41,320	$ 39,655
Tier 1 leverage capital	41,320	39,655
Risk-based capital:
Tier 1	41,320	39,655
Total risk-based capital	$ 43,762	$ 42,944
Bank actual capital ratio
Common equity Tier 1 capital ratio, Actual, Ratio (as a percent)	13.45%	13.91%
Tier 1 leverage capital ratio (as a percent)	8.80%	9.59%
Risk-based capital:
Tier 1 (as a percent)	13.45%	13.91%
Total (as a percent)	14.24%	15.06%
Minimum capital adequacy amount
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Amount	$ 13,825	$ 12,829
Tier 1 leverage capital	18,782	16,540
Risk-based capital:
Tier 1	18,433	17,105
Total	$ 24,585	$ 22,812
Minimum capital adequacy ratio
Common equity Tier 1 capital ratio, Minimum Required for Capital Adequacy Purposes, Ratio (as a percent)	4.50%	4.50%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	6.00%	6.00%
Total (as a percent)	8.00%	8.00%
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio	$ 21,505	$ 19,956
Tier 1 leverage capital ratio	18,782	16,540
Risk-based capital:
Tier 1 risk-based capital ratio	26,113	24,232
Total risk-based capital ratio	$ 32,268	$ 29,941
Minimum Required for Fully Phased in Capital Adequacy Purposes plus Capital Conservation Buffer
Common equity Tier 1 capital ratio (as a percent)	7.00%	7.00%
Tier 1 leverage capital ratio (as a percent)	4.00%	4.00%
Risk-based capital:
Tier 1 (as a percent)	8.50%	8.50%
Total (as a percent)	10.50%	10.50%
Classified as well capitalized
Common equity Tier 1 capital ratio, Minimum Required to Be Considered Well-Capitalized, Amount	$ 19,969	$ 18,530
Tier 1 leverage capital	23,477	20,675
Risk-based capital:
Tier 1	24,577	22,807
Total	$ 30,732	$ 28,515
Classified as well capitalized ratio
Common equity Tier 1 capital ratio, Minimum Required to Be Considered Well-Capitalized, Ratio (as a percent)	6.50%	6.50%
Tier 1 leverage capital ratio (as a percent)	5.00%	5.00%
Risk-based capital:
Tier 1 (as a percent)	8.00%	8.00%
Total (as a percent)	10.00%	10.00%

Employee Benefit Plans (Rollfor

Employee Benefit Plans (Rollforward of Plan Assets and Benefit Obligation) (Details) - Health Insurance Postretirement Benefit - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in plan assets:
Fair value of plan assets at beginning of year	$ 0	$ 0	$ 0
Employer contributions	32	31	19
Benefits paid	(32)	(31)	(19)
Fair value of plan assets at end of year	0	0	0
Change in benefit obligation:
Benefit obligation at beginning of year	1,490	1,534	1,135
Service cost	54	70	49
Interest cost	60	59	43
Estimated benefits paid	(32)	(31)	(19)
Actuarial loss (gain)	185	(142)	326
Benefit obligation at end of year	1,757	1,490	1,534
Funded status at end of year	1,757	1,490	1,534
Accumulated benefit obligation at end of year	$ 1,757	$ 1,490	$ 1,534

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019USD ($)participantfinancial_institutionyrplanshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of 401(k) plans administered | plan	1
Minimum employee age required to participate in the plan (in years) | yr	21
Expense for the company plan contributions	$ 3,100,000	$ 3,200,000	$ 2,600,000
Expense with deferred compensation plan	236,200	181,100	128,500
Accrued liabilities with deferred compensation plan	$ 5,500	$ 5,500	80,200
Number of supplemental executive retirement plans | plan	2
Unallocated shares | shares	79,548	109,950
Unallocated shares, aggregate cost	$ 433,000	$ 599,000
ESOP shares committed to be released	$ 458,000	$ 543,000	$ 501,000
Granted (in shares) | shares	0	0	0
401(k) plan 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company contribution as percentage of compensation of eligible employees	5.00%
Health Insurance Postretirement Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Aggregate benefits payable included in accrued expenses and other liabilities	$ 1,800,000	$ 1,500,000	$ 1,500,000
Discount rate used to determine the actuarial present value of projected postretirement benefit obligations (as a percent)	3.19%	4.22%	3.62%
Estimated prior service credit that will be amortized from accumulated other comprehensive income into net periodic benefit cost	$ 100,000
Assumed health care trend rates used in 2019 through 2023, high end of range (as a percent)	5.90%
Assumed health care trend rates used in 2019 through 2023, low end of range (as a percent)	5.10%
Ultimate health care trend rate after 2020 (as a percent)	4.50%
Expenses for benefits payable recognized under agreement	$ 66,000	$ 108,000	$ 24,000
Supplemental retirement plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Aggregate benefits payable included in accrued expenses and other liabilities	$ 12,800,000	12,100,000
Number of participants | participant	13
Expenses for benefits payable recognized under agreement	$ 1,100,000	$ 500,000
Discount rate used to determine the actuarial present value (as a percent)	3.25%	4.00%
Below age 65 | Health Insurance Postretirement Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual health care trend that will be used to measure the accumulated postretirement benefit obligation (as a percent)	13.30%
Actual health care trend used to measure the accumulated postretirement benefit obligation (as a percent)		3.10%
Over age 65 | Health Insurance Postretirement Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual health care trend that will be used to measure the accumulated postretirement benefit obligation (as a percent)	1.20%
Actual health care trend used to measure the accumulated postretirement benefit obligation (as a percent)		2.40%
Employee Stock Ownership Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
ESOP loan to purchase shares of entity's common stock | shares	546,986
Number of years during which quarterly installments are payable	30 years
Percentage of interest payable per annum on loan obtained by the ESOP	8.50%
Outstanding balance of loan	$ 800,000	$ 1,000,000
Unallocated shares | shares	79,548	109,950
Unallocated shares, aggregate cost	$ 400,000	$ 600,000
Unallocated shares, market value	1,300,000	$ 1,500,000
ESOP shares committed to be released	$ 500,000
Number of shares committed to be released to eligible employees | shares	30,402	32,382	34,356
2011 Restricted Stock Award Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of authorized shares | shares	500,000
Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of authorized shares | shares	1,750,000
Share-based compensation expense	$ 2,400,000	$ 2,500,000	$ 2,300,000
Tax benefits from vested awards	$ 100,000	1,200,000	700,000
Performance-based shares
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of financial institutions comprising peer group | financial_institution	17
Restricted stock
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Dividends paid on unvested shares recognized as compensation expense	$ 100,000	200,000	100,000
Stock Options
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Share-based compensation expense	$ 0	0	0
Exercisable period upon happening of a specific event, low end of range (in months)	3 months
Exercisable period upon happening of a specific event, high end of range (in years)	5 years
Dividend equivalent rights	$ 0	$ 0	$ 0
Vesting equally over three years | Time-based shares
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent of shares in tranche	50.00%
Award vesting period	3 years
Vesting percentage	33.00%
Vesting after achievement of performance targets | Performance-based shares
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent of shares in tranche	50.00%
Award vesting period	3 years

Employee Benefit Plans (Compone

Employee Benefit Plans (Components of Net Periodic Postretirement Benefit Costs and Other Amounts Recognized in OCI) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in postretirement benefit obligation recognized in other comprehensive income:
Total pre-tax changes in postretirement benefit obligation recognized in other comprehensive income	$ (227)	$ 121	$ (422)
Health Insurance Postretirement Benefit
Net periodic benefit expense:
Service cost	54	70	49
Interest cost	60	59	43
Prior service credit	(21)	(21)	(21)
Actuarial gain	(27)	0	(47)
Net periodic benefit expense	66	108	24
Changes in postretirement benefit obligation recognized in other comprehensive income:
Net actuarial (loss) gain	(206)	142	(401)
Prior service credit	(21)	(21)	(21)
Total pre-tax changes in postretirement benefit obligation recognized in other comprehensive income	$ (227)	$ 121	$ (422)

Employee Benefit Plans (Effects

Employee Benefit Plans (Effects of Changes in Assumed Healthcare Cost Trends) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Effect of 1% change in assumed health care cost trend rates
Effect of 1% increase on total service and interest cost components of net periodic postretirement benefit costs	$ 25
Effect of 1% decrease on total service and interest cost components of net periodic postretirement benefit costs	(20)
Effect of 1% increase on the accumulated postretirement benefit obligation	365
Effect of 1% decrease on the accumulated postretirement benefit obligation	$ (289)

Employee Benefit Plans (Activit

Employee Benefit Plans (Activity in Recognition and Retention Plans) (Details) - Restricted stock $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)$ / sharesshares
Restricted Stock Awards Outstanding
Outstanding at beginning of year (in shares) | shares	390,635
Granted (in shares) | shares	212,461
Vested (in shares) | shares	(175,160)
Forfeited / Canceled (in shares) | shares	(21,486)
Outstanding at end of year (in shares) | shares	406,450
Weighted Average Grant Price per Share
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 15.21
Granted (in dollars per share) | $ / shares	14.25
Vested (in dollars per share) | $ / shares	14.46
Forfeited / Canceled (in dollars per share) | $ / shares	11.78
Outstanding at end of year (in dollars per share) | $ / shares	$ 15.21
Unrecognized compensation cost | $	$ 3,964
Weighted average remaining recognition period	24 months

Employee Benefit Plans (Activ_2

Employee Benefit Plans (Activity in Option Plans) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock option activity
Outstanding at the beginning of the period (in shares)	5,000
Granted (in shares)	0	0	0
Exercised (in shares)	0
Forfeited/Canceled (in shares)	0
Outstanding at the end of the period (in shares)	5,000	5,000
Exercisable at the end of the period (in shares)	5,000
Stock Option Activity, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 9.90
Granted (in dollars per share)	0
Exercised (in dollars per share)	0
Forfeited/Canceled (in dollars per share)	0
Outstanding at the end of the period (in dollars per share)	9.90	$ 9.90
Exercisable at the end of the period (in dollars per share)	$ 9.90
Stock Option Activity, Aggregate Intrinsic Value
Outstanding at the end of the period	$ 33
Exercisable at the end of the period	$ 33
Stock Option Activity, Weighted Average Contractual Term
Outstanding at the end of the period (in years)	24 days
Exercisable at the end of the period (in years)	24 days
Options exercisable period	10 years

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Assets and Liabilities Recorded at Fair Value on a Recurring Basis) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Assets:
AFS, debt securities, estimated fair value	$ 498,995,000	$ 502,793,000
Investment securities available-for-sale		502,793,000
Equity securities held-for-trading	3,581,000	4,207,000
Derivatives	60,648,000	22,488,000
Liabilities:
Derivatives	59,701,000	22,220,000
GSE debentures
Assets:
AFS, debt securities, estimated fair value	185,803,000	181,079,000
GSE CMOs
Assets:
AFS, debt securities, estimated fair value	85,932,000	103,130,000
GSE MBSs
Assets:
AFS, debt securities, estimated fair value	153,343,000	165,089,000
SBA commercial loan asset-backed securities
Assets:
AFS, debt securities, estimated fair value	34,000	51,000
Corporate debt obligations
Assets:
AFS, debt securities, estimated fair value	28,986,000	39,708,000
U.S. treasury bonds
Assets:
AFS, debt securities, estimated fair value	44,897,000	13,736,000
Recurring basis
Assets:
AFS, debt securities, estimated fair value	498,995,000
Investment securities available-for-sale		502,793,000
Equity securities held-for-trading	3,581,000	4,207,000
Liabilities:
Derivatives	59,365,000
Recurring basis | GSE debentures
Assets:
AFS, debt securities, estimated fair value	185,803,000	181,079,000
Recurring basis | GSE CMOs
Assets:
AFS, debt securities, estimated fair value	85,932,000	103,130,000
Recurring basis | GSE MBSs
Assets:
AFS, debt securities, estimated fair value	153,343,000	165,089,000
Recurring basis | SBA commercial loan asset-backed securities
Assets:
AFS, debt securities, estimated fair value	34,000	51,000
Recurring basis | Corporate debt obligations
Assets:
AFS, debt securities, estimated fair value	28,986,000	39,708,000
Recurring basis | U.S. treasury bonds
Assets:
AFS, debt securities, estimated fair value	44,897,000	13,736,000
Recurring basis | Loan level derivatives
Assets:
Derivatives	59,365,000	22,013,000
Liabilities:
Derivatives		22,013,000
Recurring basis | Risk participation-out agreements
Assets:
Derivatives	1,229,000	344,000
Recurring basis | Risk participation-in agreements
Liabilities:
Derivatives	283,000	84,000
Recurring basis | Foreign exchange contracts
Assets:
Derivatives	54,000	131,000
Liabilities:
Derivatives	53,000	123,000
Recurring basis | Level 1
Assets:
AFS, debt securities, estimated fair value	0
Investment securities available-for-sale		0
Equity securities held-for-trading	2,569,000	3,235,000
Liabilities:
Derivatives	0
Recurring basis | Level 1 | GSE debentures
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 1 | GSE CMOs
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 1 | GSE MBSs
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 1 | SBA commercial loan asset-backed securities
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 1 | Corporate debt obligations
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 1 | U.S. treasury bonds
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 1 | Loan level derivatives
Assets:
Derivatives	0	0
Liabilities:
Derivatives		0
Recurring basis | Level 1 | Risk participation-out agreements
Assets:
Derivatives	0	0
Recurring basis | Level 1 | Risk participation-in agreements
Liabilities:
Derivatives	0	0
Recurring basis | Level 1 | Foreign exchange contracts
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Recurring basis | Level 2
Assets:
AFS, debt securities, estimated fair value	498,995,000
Investment securities available-for-sale		502,793,000
Equity securities held-for-trading	1,012,000	972,000
Liabilities:
Derivatives	59,365,000
Recurring basis | Level 2 | GSE debentures
Assets:
AFS, debt securities, estimated fair value	185,803,000	181,079,000
Recurring basis | Level 2 | GSE CMOs
Assets:
AFS, debt securities, estimated fair value	85,932,000	103,130,000
Recurring basis | Level 2 | GSE MBSs
Assets:
AFS, debt securities, estimated fair value	153,343,000	165,089,000
Recurring basis | Level 2 | SBA commercial loan asset-backed securities
Assets:
AFS, debt securities, estimated fair value	34,000	51,000
Recurring basis | Level 2 | Corporate debt obligations
Assets:
AFS, debt securities, estimated fair value	28,986,000	39,708,000
Recurring basis | Level 2 | U.S. treasury bonds
Assets:
AFS, debt securities, estimated fair value	44,897,000	13,736,000
Recurring basis | Level 2 | Loan level derivatives
Assets:
Derivatives	59,365,000	22,013,000
Liabilities:
Derivatives		22,013,000
Recurring basis | Level 2 | Risk participation-out agreements
Assets:
Derivatives	1,229,000	344,000
Recurring basis | Level 2 | Risk participation-in agreements
Liabilities:
Derivatives	283,000	84,000
Recurring basis | Level 2 | Foreign exchange contracts
Assets:
Derivatives	54,000	131,000
Liabilities:
Derivatives	53,000	123,000
Recurring basis | Level 3
Assets:
AFS, debt securities, estimated fair value	0
Investment securities available-for-sale		0
Equity securities held-for-trading	0	0
Liabilities:
Derivatives	0
Recurring basis | Level 3 | GSE debentures
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 3 | GSE CMOs
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 3 | GSE MBSs
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 3 | SBA commercial loan asset-backed securities
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 3 | Corporate debt obligations
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 3 | U.S. treasury bonds
Assets:
AFS, debt securities, estimated fair value	0	0
Recurring basis | Level 3 | Loan level derivatives
Assets:
Derivatives	0	0
Liabilities:
Derivatives		0
Recurring basis | Level 3 | Risk participation-out agreements
Assets:
Derivatives	0	0
Recurring basis | Level 3 | Risk participation-in agreements
Liabilities:
Derivatives	0	0
Recurring basis | Level 3 | Foreign exchange contracts
Assets:
Derivatives	0	0
Liabilities:
Derivatives	$ 0	$ 0

Fair Value of Financial Instr_4

Fair Value of Financial Instruments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Changes in generic pricing of securities period one, considered for analyzing changes in prices obtained from pricing service (in years)	15 years
Changes in generic pricing of securities period two, considered for analyzing changes in prices obtained from pricing service (in years)	30 years

Fair Value of Financial Instr_5

Fair Value of Financial Instruments (Assets and Liabilities Recorded at Fair Value on a Non-Recurring Basis) (Details) - Nonrecurring basis - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	$ 4,874	$ 15,470
Level 1
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	0	0
Level 2
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	2,631	965
Level 3
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	2,243	14,505
Collateral-dependent impaired loans and leases
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	2,243	11,451
Collateral-dependent impaired loans and leases | Level 1
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	0	0
Collateral-dependent impaired loans and leases | Level 2
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	0	0
Collateral-dependent impaired loans and leases | Level 3
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	2,243	11,451
OREO
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis		3,054
OREO | Level 1
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis		0
OREO | Level 2
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis		0
OREO | Level 3
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis		3,054
Repossessed assets
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	2,631	965
Repossessed assets | Level 1
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	0	0
Repossessed assets | Level 2
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	2,631	965
Repossessed assets | Level 3
Fair value of assets and liabilities
Total assets measured at fair value on a non-recurring basis	$ 0	$ 0

Fair Value of Financial Instr_6

Fair Value of Financial Instruments (Repossessed Assets) (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Recurring basis | Collateral-dependent impaired loans and leases | Appraisal of collateral
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value of assets	$ 2,243	$ 11,451
Recurring basis | Other real estate owned | Appraisal of collateral
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value of assets	$ 0	$ 3,054
Minimum | Discount for Costs to Sell
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value inputs, basis spread (as a percent)	0.00%
Minimum | Appraisal Adjustments
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value inputs, basis spread (as a percent)	0.00%
Maximum | Discount for Costs to Sell
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value inputs, basis spread (as a percent)	10.00%
Maximum | Appraisal Adjustments
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value inputs, basis spread (as a percent)	15.00%

Fair Value of Financial Instr_7

Fair Value of Financial Instruments (Summary of Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets:
Investment securities held-to-maturity:	$ 87,561	$ 112,830
Loans and leases, net	6,676,734	6,244,824
Restricted equity securities	53,818	61,751
Financial liabilities:
Certificates of deposit	2,021,642	1,789,165
Borrowed funds	60,689	52,734
Level 1
Financial assets:
Loans held-for-sale		0
Loans and leases, net	0	0
Restricted equity securities	0	0
Financial liabilities:
Certificates of deposit	0	0
Borrowed funds	0	0
Level 2
Financial assets:
Loans held-for-sale		3,247
Loans and leases, net	0	0
Restricted equity securities	0	0
Financial liabilities:
Certificates of deposit	2,026,683	1,778,860
Borrowed funds	902,670	886,545
Level 3
Financial assets:
Loans held-for-sale		0
Loans and leases, net	6,697,583	6,154,704
Restricted equity securities	53,818	61,751
Financial liabilities:
Certificates of deposit	0	0
Borrowed funds	0	0
Carrying Value
Financial assets:
Loans held-for-sale		3,247
Loans and leases, net	6,676,734	6,244,824
Restricted equity securities	53,818	61,751
Financial liabilities:
Certificates of deposit	2,021,642	1,789,165
Borrowed funds	902,749	920,542
Estimated Fair Value
Financial assets:
Loans held-for-sale		3,247
Loans and leases, net	6,697,583	6,154,704
Restricted equity securities	53,818	61,751
Financial liabilities:
Certificates of deposit	2,026,683	1,778,860
Borrowed funds	902,670	886,545
GSE debentures
Financial assets:
Investment securities held-to-maturity:	31,290	49,601
GSE debentures | Level 1
Financial assets:
Investment securities held-to-maturity:	0	0
GSE debentures | Level 2
Financial assets:
Investment securities held-to-maturity:	31,290	49,601
GSE debentures | Level 3
Financial assets:
Investment securities held-to-maturity:	0	0
GSE debentures | Carrying Value
Financial assets:
Investment securities held-to-maturity:	31,228	50,546
GSE debentures | Estimated Fair Value
Financial assets:
Investment securities held-to-maturity:	31,290	49,601
GSE MBSs
Financial assets:
Investment securities held-to-maturity:	9,279	11,131
GSE MBSs | Level 1
Financial assets:
Investment securities held-to-maturity:	0	0
GSE MBSs | Level 2
Financial assets:
Investment securities held-to-maturity:	9,279	11,131
GSE MBSs | Level 3
Financial assets:
Investment securities held-to-maturity:	0	0
GSE MBSs | Carrying Value
Financial assets:
Investment securities held-to-maturity:	9,360	11,426
GSE MBSs | Estimated Fair Value
Financial assets:
Investment securities held-to-maturity:	9,279	11,131
Municipal obligations
Financial assets:
Investment securities held-to-maturity:	46,514	51,598
Municipal obligations | Level 1
Financial assets:
Investment securities held-to-maturity:	0	0
Municipal obligations | Level 2
Financial assets:
Investment securities held-to-maturity:	46,514	51,598
Municipal obligations | Level 3
Financial assets:
Investment securities held-to-maturity:	0	0
Municipal obligations | Carrying Value
Financial assets:
Investment securities held-to-maturity:	45,692	52,304
Municipal obligations | Estimated Fair Value
Financial assets:
Investment securities held-to-maturity:	46,514	51,598
Foreign government obligations
Financial assets:
Investment securities held-to-maturity:	478	500
Foreign government obligations | Level 1
Financial assets:
Investment securities held-to-maturity:	0	0
Foreign government obligations | Level 2
Financial assets:
Investment securities held-to-maturity:	0	0
Foreign government obligations | Level 3
Financial assets:
Investment securities held-to-maturity:	478	500
Foreign government obligations | Carrying Value
Financial assets:
Investment securities held-to-maturity:	500	500
Foreign government obligations | Estimated Fair Value
Financial assets:
Investment securities held-to-maturity:	$ 478	$ 500

Condensed Parent Company Fina_3

Condensed Parent Company Financial Statements (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and due from banks	$ 33,589	$ 47,542
Short-term investments	44,201	42,042
Total cash and cash equivalents	77,790	89,584
Equity securities held-for-trading	3,581	4,207
Restricted equity securities	53,818	61,751
Premises and equipment, net	74,350	76,382
Deferred tax asset	25,017	21,495
Goodwill	160,427	160,427	$ 137,890	$ 137,890
Other assets	167,431	103,214
Total assets	7,856,853	7,392,805
LIABILITIES AND STOCKHOLDERS' EQUITY
Borrowed funds	902,749	920,542
Accrued expenses and other liabilities	146,318	100,174
Total liabilities	6,911,247	6,482,186
Stockholders' Equity:
Common stock, $0.01 par value; 200,000,000 shares authorized; 85,177,172 shares issued and 85,177,172 shares issued, respectively	852	852
Additional paid-in capital	736,601	755,629
Retained earnings, partially restricted	265,376	212,838
Accumulated other comprehensive loss	2,283	(9,460)
Treasury stock, at cost; 5,003,127 shares and 5,020,025 shares, respectively	(59,073)	(59,120)
Unallocated common stock held by ESOP; 79,548 shares and 109,950 shares, respectively	(433)	(599)
Total Brookline Bancorp, Inc. stockholders' equity	945,606	900,140
Total liabilities and stockholders' equity	7,856,853	7,392,805
Parent Company
ASSETS
Cash and due from banks	35,736	33,663
Short-term investments	33	33
Total cash and cash equivalents	35,769	33,696	$ 5,543	$ 32,252
Equity securities held-for-trading	2,569	3,235
ESOP loan to Brookline Bank	752	1,002
Intercompany loan to Brookline Bank	30,000	40,000
Restricted equity securities	252	101
Premises and equipment, net	2,403	4,318
Deferred tax asset	1,742	1,499
Investment in subsidiaries, at equity	924,352	864,798
Goodwill	35,267	35,267
Other assets	12,116	5,400
Total assets	1,045,222	989,316
LIABILITIES AND STOCKHOLDERS' EQUITY
Borrowed funds	83,591	83,433
Deferred tax liability	0	0
Accrued expenses and other liabilities	16,025	5,743
Total liabilities	99,616	89,176
Stockholders' Equity:
Common stock, $0.01 par value; 200,000,000 shares authorized; 85,177,172 shares issued and 85,177,172 shares issued, respectively	852	852
Additional paid-in capital	736,601	755,629
Retained earnings, partially restricted	265,376	212,838
Accumulated other comprehensive loss	2,283	(9,460)
Treasury stock, at cost; 5,003,127 shares and 5,020,025 shares, respectively	(59,073)	(59,120)
Unallocated common stock held by ESOP; 79,548 shares and 109,950 shares, respectively	(433)	(599)
Total Brookline Bancorp, Inc. stockholders' equity	945,606	900,140
Total liabilities and stockholders' equity	$ 1,045,222	$ 989,316

Condensed Parent Company Fina_4

Condensed Parent Company Financial Statements (Condensed Balance Sheets (Additional Information)) (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	85,177,172	85,177,172
Treasury stock, shares	5,003,127	5,020,025
Unallocated common stock held by ESOP, shares	79,548	109,950
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	85,177,172	85,177,172
Treasury stock, shares	5,003,127	5,020,025
Unallocated common stock held by ESOP, shares	79,548	109,950

Condensed Parent Company Fina_5

Condensed Parent Company Financial Statements (Condensed Income Statements) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest and dividend income:
Marketable and restricted equity securities									$ 3,477	$ 3,964	$ 3,062
Total interest and dividend income	$ 87,450	$ 87,906	$ 87,184	$ 85,086	$ 83,544	$ 80,636	$ 78,074	$ 71,639	347,626	313,893	263,050
Interest expense:
Net interest income	63,931	63,236	63,134	62,999	63,159	62,332	62,717	59,491	253,300	247,699	223,181
Gain on investment securities, net	133	(116)	357	134	(692)	(243)	0	1,162	508	227	11,393
Non-interest income:
Other									6,594	5,847	4,789
Total non-interest income									29,793	25,224	32,173
Non-interest expense:
Compensation and employee benefits									96,554	91,535	82,413
Occupancy									15,696	14,991	14,546
Equipment and data processing									18,652	18,213	16,854
Professional services									4,366	4,404	4,315
Advertising and marketing									4,044	4,016	3,369
Merger and acquisition expense									1,125	3,787	411
Other	38,395	39,770	39,184	38,469	39,745	36,773	37,163	39,471	13,936	13,484	11,788
Total non-interest expense									157,481	155,232	139,111
Credit for income taxes	7,087	7,507	6,780	6,895	7,055	6,140	7,342	5,652	28,269	26,189	43,636
Net income attributable to Brookline Bancorp, Inc.	$ 22,183	$ 22,596	$ 20,471	$ 22,467	$ 21,138	$ 22,460	$ 20,831	$ 18,633	87,717	83,062	50,518
Parent Company
Interest and dividend income:
Dividend income from subsidiaries									0	0	7,317
Marketable and restricted equity securities									147	37	0
ESOP loan to Brookline Bank									77	98	120
Intercompany loan to Brookline Bank									1,183	1,722	532
Total interest and dividend income									1,407	1,857	7,969
Interest expense:
Borrowed funds									5,274	5,223	5,123
Net interest income									(3,867)	(3,366)	2,846
Gain on investment securities, net									467	71	0
Non-interest income:
Other									0	16	0
Total non-interest income									467	87	0
Non-interest expense:
Compensation and employee benefits									(507)	345	391
Occupancy									1,589	1,586	1,584
Equipment and data processing									(770)	(798)	(1,011)
Directors' fees									461	417	453
Franchise taxes									306	321	180
Insurance									543	534	528
Professional services									548	364	470
Advertising and marketing									31	19	4
Merger and acquisition expense									0	452	411
Other									(1,139)	(1,140)	(1,224)
Total non-interest expense									1,062	2,100	1,786
Loss before income taxes									(4,462)	(5,379)	1,060
Credit for income taxes									(969)	(1,976)	(1,944)
Loss before equity in undistributed income of subsidiaries									(3,493)	(3,403)	3,004
Equity in undistributed income of subsidiaries									91,210	86,465	47,514
Net income attributable to Brookline Bancorp, Inc.									$ 87,717	$ 83,062	$ 50,518

Condensed Parent Company Fina_6

Condensed Parent Company Financial Statements (Condensed Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income attributable to Brookline Bancorp, Inc.	$ 22,183	$ 22,596	$ 20,471	$ 22,467	$ 21,138	$ 22,460	$ 20,831	$ 18,633	$ 87,717	$ 83,062	$ 50,518
Adjustments to reconcile net income to net cash provided from operating activities:
Depreciation of premises and equipment									6,861	7,382	7,232
Amortization of debt issuance costs									100	100	100
Equity securities held-for-trading									1,215	(5,371)	0
Net cash provided from operating activities									102,719	123,029	84,947
Cash flows from investing activities:
Purchase of restricted equity securities									(12,924)	(13,262)	(7,927)
Purchase of premises and equipment									(4,997)	(3,352)	(11,557)
Net cash used for investing activities									(399,022)	(588,022)	(383,974)
Cash flows from financing activities:
Proceeds from issuance of common stock									0	0	81,943
Common stock issued for acquisition									0	55,182	0
Redemption of noncontrolling interest in subsidiary									(35,851)	0	0
Payment of dividends to owners of noncontrolling interest in subsidiary									(930)	(1,893)	(1,671)
Payment of dividends on common stock									(35,110)	(31,441)	(27,035)
Net cash provided from financing activities									284,509	493,572	292,375
Cash and cash equivalents at beginning of year				89,584					89,584
Cash and cash equivalents at end of year	77,790				89,584				77,790	89,584
Parent Company
Cash flows from operating activities:
Net income attributable to Brookline Bancorp, Inc.									87,717	83,062	50,518
Adjustments to reconcile net income to net cash provided from operating activities:
Equity in undistributed income of subsidiaries									(91,210)	(86,465)	(47,514)
Depreciation of premises and equipment									2,824	3,073	2,856
Amortization of debt issuance costs									100	100	100
Equity securities held-for-trading									666	(3,235)	0
Other operating activities, net									47,296	(31,014)	(5,885)
Net cash provided from operating activities									47,393	(34,479)	75
Cash flows from investing activities:
Repayment of ESOP loan by Brookline Bank									250	250	250
Pay down (issuance) of intercompany loan to Brookline Bank									10,000	40,000	(80,000)
Purchase of restricted equity securities									(151)	(1)	0
Purchase of premises and equipment									(909)	(1,359)	(1,942)
Net cash used for investing activities									9,190	38,890	(81,692)
Cash flows from financing activities:
Proceeds from issuance of common stock									0	0	81,943
Common stock issued for acquisition									0	55,183	0
Redemption of noncontrolling interest in subsidiary									(18,470)	0	0
Payment of dividends to owners of noncontrolling interest in subsidiary									(930)	0	0
Payment of dividends on common stock									(35,110)	(31,441)	(27,035)
Net cash provided from financing activities									(54,510)	23,742	54,908
Net increase (decrease) in cash and cash equivalents									2,073	28,153	(26,709)
Cash and cash equivalents at beginning of year				$ 33,696				$ 5,543	33,696	5,543	32,252
Cash and cash equivalents at end of year	$ 35,769				$ 33,696				35,769	33,696	5,543
Supplemental disclosures of cash flow information:
Fair value of assets acquired, net of cash and cash equivalents acquired									0	292,025	0
Fair value of liabilities assumed									$ 0	$ 278,988	$ 0

Quarterly Results of Operatio_3

Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interest and dividend income	$ 87,450	$ 87,906	$ 87,184	$ 85,086	$ 83,544	$ 80,636	$ 78,074	$ 71,639	$ 347,626	$ 313,893	$ 263,050
Interest expense	23,519	24,670	24,050	22,087	20,385	18,304	15,357	12,148	94,326	66,194	39,869
Net interest income	63,931	63,236	63,134	62,999	63,159	62,332	62,717	59,491	253,300	247,699	223,181
Provision for credit losses	3,602	871	3,757	1,353	123	2,717	1,470	641	9,583	4,951	18,988
Net interest income after provision for credit losses	60,329	62,365	59,377	61,646	63,036	59,615	61,247	58,850	243,717	242,748	204,193
Loan level derivative income, net	2,494	2,251	1,772	1,745	1,811	2,192	571	866	8,262	5,440	2,187
(Loss) gain on investment securities, net	133	(116)	357	134	(692)	(243)	0	1,162	508	227	11,393
Gain on sales of loans and leases held-for-sale	309	550	561	289	327	535	722	299	1,709	1,883	2,644
Other non-interest income	4,820	5,244	4,788	4,462	5,015	4,585	4,233	3,841
Amortization of identified intangible assets	(420)	(421)	(420)	(402)	(537)	(537)	(539)	(467)	(1,663)	(2,080)	(2,089)
Other non-interest expense	(38,395)	(39,770)	(39,184)	(38,469)	(39,745)	(36,773)	(37,163)	(39,471)	(13,936)	(13,484)	(11,788)
Income before provision for income taxes	29,270	30,103	27,251	29,405	29,215	29,374	29,071	25,080	116,029	112,740	97,255
Provision for income taxes	7,087	7,507	6,780	6,895	7,055	6,140	7,342	5,652	28,269	26,189	43,636
Net income before noncontrolling interest in subsidiary	22,183	22,596	20,471	22,510	22,160	23,234	21,729	19,428	87,760	86,551	53,619
Less net income attributable to noncontrolling interest in subsidiary	0	0	0	43	1,022	774	898	795	43	3,489	3,101
Net income attributable to Brookline Bancorp, Inc.	$ 22,183	$ 22,596	$ 20,471	$ 22,467	$ 21,138	$ 22,460	$ 20,831	$ 18,633	$ 87,717	$ 83,062	$ 50,518
Earnings per share:
Basic (in dollars per share)	$ 0.28	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.24	$ 1.10	$ 1.04	$ 0.68
Diluted (in dollars per share)	$ 0.28	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.28	$ 0.26	$ 0.24	$ 1.10	$ 1.04	$ 0.68
Average common shares outstanding:
Basic (in shares)	79,682,724	79,700,403	79,669,922	79,658,583	80,258,489	80,315,050	80,184,977	77,879,593	79,679,781	79,669,668	74,459,508
Diluted (in shares)	79,845,447	79,883,510	79,886,292	79,843,578	80,407,558	80,515,467	80,505,614	78,167,800	79,856,921	79,909,251	74,811,408
Common stock price:
High (in dollars per share)	$ 16.83	$ 15.39	$ 15.92	$ 16.23	$ 16.97	$ 19.05	$ 19.25	$ 17.05
Low (in dollars per share)	14.36	13.73	14.35	13.90	12.86	16.70	15.90	15.60
Dividends paid:
Dividends per share (in dollars per share)	$ 0.115	$ 0.110	$ 0.110	$ 0.105	$ 0.105	$ 0.100	$ 0.100	$ 0.090	$ 0.44	$ 0.395	$ 0.360