CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
INTEREST AND DIVIDEND INCOME:
Loans, including related fees	$ 137,241	$ 124,788	$ 100,541
Securities:
Taxable	13,625	15,191	16,942
Tax-exempt	7,952	7,674	7,455
Other	1,667	1,468	1,286
TOTAL INTEREST AND DIVIDEND INCOME	160,485	149,121	126,224
INTEREST EXPENSE:
Interest Expense, Deposits	12,801	15,711	9,032
Short-term borrowings	568	1,105	501
Other borrowings	770	653	112
TOTAL INTEREST EXPENSE	14,139	17,469	9,645
NET INTEREST INCOME	146,346	131,652	116,579
Provision for credit loss expense	10,528	4,700	5,768
NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES	135,818	126,952	110,811
Trust And Financial Services Revenue	5,423	5,036	5,286
Service Charges And Fees On Deposit Accounts	10,256	11,795	11,733
Service Charges And Fees, Other	15,644	14,012	13,012
NON-INTEREST INCOME:
Securities gain (loss), net	233	44	2
Insurance commissions	158	133	144
Gain on sale of mortgage loans	6,626	2,573	1,829
Other	4,136	4,859	6,200
TOTAL NON-INTEREST INCOME	42,476	38,452	38,206
Labor and Related Expense	61,931	54,827	50,658
NON-INTEREST EXPENSES:
Occupancy expense	8,202	7,600	7,030
Equipment expense	10,568	8,244	6,827
Federal Deposit Insurance	316	693	929
Other	31,741	33,041	25,845
TOTAL NON-INTEREST EXPENSE	112,758	104,405	91,289
INCOME BEFORE INCOME TAXES	65,536	60,999	57,728
Provision for income taxes	11,692	12,127	11,145
NET INCOME	53,844	48,872	46,583
OTHER COMPREHENSIVE INCOME
Change in unrealized gains/losses on securities, net of reclassifications and taxes	19,269	20,998	(8,861)
Change in funded status of post-retirement benefits, net of taxes	(2,004)	(5,045)	2,477
COMPREHENSIVE INCOME	$ 71,109	$ 64,825	$ 40,199
EARNINGS PER SHARE:
BASIC AND DILUTED (in dollars per share)	$ 3.93	$ 3.80	$ 3.80
Weighted average number of shares outstanding (in shares)	13,716	12,865	12,256