Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 42,209	$ 39,699	$ 36,213
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Gain on sales of mortgage loans		(412)
Loss on sales of other real estate owned		79
Net gains on sales of securities	0	(61)	(302)
Net (gain) loss on equity securities	20	(92)	67
Provision for loan losses	5,825	1,250	1,350
Deferred tax (expense) benefit	(1,089)	(2,135)	(1,766)
Net depreciation and amortization	(1,070)	(2,382)	885
(Increase) decrease in accrued interest receivable	(173)	1,296	(3,227)
Decrease in other assets	(413)	8,532	2,326
(Decrease) increase in other liabilities	(934)	2,075	5,242
Net cash provided by operating activities	44,375	47,849	40,788
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from redemptions of Federal Home Loan Bank of Boston stock	10,836	14,380	18,388
Purchase of Federal Home Loan Bank of Boston stock	(4,726)	(15,877)	(14,583)
Proceeds from calls/maturities of securities available-for-sale	86,691	144,739	215,406
Proceeds from sales of securities available-for-sale		16,285	27,517
Purchase of securities available-for-sale	(107,744)	(85,123)	(183,588)
Proceeds from calls/maturities of securities held-to-maturity	902,981	458,915	234,741
Purchase of securities held-to-maturity	(1,056,023)	(757,997)	(576,140)
Proceeds from sales of securities held-to-maturity	3,900	1,193
Proceeds from life insurance policies		5,461	375
Proceeds from sales of portfolio loans		22,120
Net increase in loans	(569,595)	(162,415)	(110,874)
Bank owned life insurance purchases	(8,731)	(33,664)
Proceeds from sales of other real estate owned		2,146
Capital expenditures	(8,376)	(13,144)	(3,601)
Net cash used in investing activities	(750,787)	(402,981)	(392,359)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net decrease in time deposit accounts	(9,304)	(5,132)	(64,782)
Net increase (decrease) in demand, savings, money market and NOW deposits	1,061,414	(1,721)	554,779
Cash dividends	(2,490)	(2,207)	(2,203)
Net (decrease) increase in securities sold under agreements to repurchase	(33,955)	111,805	(4,750)
Net (decrease) increase in other borrowed funds	(193,946)	168,577	(145,400)
Net cash provided by financing activities	821,719	271,322	337,644
Net increase (decrease) in cash and cash equivalents	115,307	(83,810)	(13,927)
Cash and cash equivalents at beginning of period	258,693	342,503	356,430
Cash and cash equivalents at end of period	374,000	258,693	342,503
Cash paid (received) during the period for:
Interest	42,655	63,345	44,289
Income tax refunds		(6,504)
Income taxes	4,300		590
Change in unrealized losses on securities available-for-sale, net of taxes	438	(314)	109
Change in unrealized losses on securities transferred to held-to-maturity, net of taxes	591	753	1,086
Pension liability adjustment, net of taxes	$ (2,920)	$ (5,789)	4,937
Transfer of loans to other real estate owned			$ 2,225