Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Cash and due from banks (Note 2)	$ 136,735	$ 44,420
Federal funds sold and interest-bearing deposits in other banks	237,265	214,273
Total cash and cash equivalents	374,000	258,693
Securities available-for-sale, amortized cost $282,273 in 2020 and $260,924 in 2019 (Notes 3, 9 and 11)	282,448	260,502
Securities held-to-maturity, fair value $2,579,103 in 2020 and $2,361,304 in 2019 (Notes 4 and 11)	2,509,088	2,351,120
Federal Home Loan Bank of Boston, stock at cost	13,361	19,471
Equity securities, cost $1,635 in 2020 and $1,635 in 2019, respectively	1,668	1,688
Loans, net:
Loans, net (Note 5)	2,995,829	2,426,119
Less: allowance for loan losses (Note 6)	35,486	29,585
Net loans	2,960,343	2,396,534
Bank premises and equipment (Note 7)	39,062	33,952
Accrued interest receivable	13,283	13,110
Other assets (Notes 5, 6, 8, 16, 17, 23)	165,581	157,354
Total assets	6,358,834	5,492,424
Deposits:
Demand deposits	1,103,878	712,842
Savings and NOW deposits	1,728,092	1,678,250
Money market accounts	2,074,108	1,453,572
Time deposits (Note 10)	546,143	555,447
Total deposits	5,452,221	4,400,111
Securities sold under agreements to repurchase (Note 11)	232,090	266,045
Other borrowed funds (Note 12)	177,009	370,955
Subordinated debentures (Note 12)	36,083	36,083
Other liabilities (Note 17)	91,022	86,649
Total liabilities	5,988,425	5,159,843
Commitments and contingencies (Notes 18 and 19)
Stockholders' equity (Note 15):
Preferred Stock – $1.00 par value; 100,000 shares authorized; no shares issued and outstanding
Additional paid-in capital	12,292	12,292
Retained earnings	378,699	338,980
Stockholders' equity before adjustment of accumulated other comprehensive income (loss)	396,559	356,840
Unrealized gains(losses) on securities available-for-sale, net of taxes	130	(308)
Unrealized losses on securities transferred to held-to-maturity, net of taxes	(1,221)	(1,812)
Pension liability, net of taxes	(25,059)	(22,139)
Total accumulated other comprehensive loss, net of taxes (Notes 3, 13 and 15)	(26,150)	(24,259)
Total stockholders' equity	370,409	332,581
Total liabilities and stockholders' equity	6,358,834	5,492,424
Class A Common Stock [Member]
Stockholders' equity (Note 15):
Common stock value	3,656	3,651
Total stockholders' equity	3,656	3,651
Class B Common Stock [Member]
Stockholders' equity (Note 15):
Common stock value	1,912	1,917
Total stockholders' equity	$ 1,912	$ 1,917