Consolidated Condensed Statements Of Income - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest and dividend income:
Interest and fees on loans	$ 78,127,000	$ 82,617,000	$ 238,040,000	$ 243,459,000
Interest and dividends on:
Obligations of U.S. Government, its agencies and other securities	4,904,000	4,841,000	13,760,000	15,398,000
Interest Income, Securities, State and Municipal	2,029,000	2,045,000	6,098,000	6,396,000
Other interest income	360,000	63,000	689,000	667,000
Total interest and dividend income	85,420,000	89,566,000	258,587,000	265,920,000
Interest on deposits:
Demand and savings deposits	435,000	803,000	1,222,000	8,652,000
Time deposits	1,011,000	2,662,000	3,880,000	10,293,000
Interest on borrowings:
Short-term borrowings	187,000	217,000	552,000	912,000
Long-term debt	2,185,000	2,044,000	6,746,000	4,754,000
Total interest expense	3,818,000	5,726,000	12,400,000	24,611,000
Net interest income	81,602,000	83,840,000	246,187,000	241,309,000
(Recovery of) provision for credit losses	1,972,000	13,836,000	(6,923,000)	31,213,000
Net interest income after provision for credit losses	79,630,000	70,004,000	253,110,000	210,096,000
Noninterest Income [Abstract]
Debit card fee income	6,453,000	5,853,000	19,297,000	16,373,000
Bank owned life insurance income	1,462,000	1,192,000	3,776,000	3,619,000
ATM Fees	622,000	491,000	1,807,000	1,341,000
Gains (Losses) on Sales of Other Real Estate	3,000	569,000	(26,000)	1,214,000
Debt Securities, Realized Gain (Loss)	0	(27,000)	0	3,286,000
(Gain) loss on equity securities, net	609,000	1,201,000	2,886,000	(749,000)
Other components of net periodic benefit income	2,038,000	1,988,000	6,114,000	5,964,000
Other	3,347,000	2,791,000	8,403,000	5,826,000
Total other income	32,411,000	36,558,000	97,738,000	90,008,000
Other expense:
Salaries and employee benefits	29,433,000	31,632,000	89,632,000	90,760,000
Employee Benefits and Share-based Compensation	10,640,000	10,676,000	30,897,000	29,799,000
Occupancy expense	3,211,000	3,835,000	9,878,000	10,571,000
Furniture and equipment expense	2,797,000	4,687,000	8,163,000	13,856,000
Data processing fees	7,817,000	3,275,000	22,679,000	8,344,000
Professional fees and services	6,973,000	7,977,000	19,610,000	21,944,000
Marketing	1,574,000	1,454,000	4,355,000	4,076,000
Insurance	1,403,000	1,541,000	4,370,000	4,568,000
Communication	796,000	958,000	2,688,000	2,987,000
Excise and Sales Taxes	1,113,000	1,125,000	3,324,000	3,386,000
Amortization of Intangible Assets	420,000	525,000	1,378,000	1,738,000
Foundation contribution expense	0	0	4,000,000	0
Other expense	2,312,000	2,174,000	6,780,000	8,905,000
Total other expense	68,489,000	69,859,000	207,754,000	200,934,000
Income before income taxes	43,552,000	36,703,000	143,094,000	99,170,000
Income taxes	8,118,000	5,857,000	25,697,000	16,447,000
Net income	$ 35,434,000	$ 30,846,000	$ 117,397,000	$ 82,723,000
Net income available to common shareholders
Basic	$ 2.17	$ 1.89	$ 7.20	$ 5.07
Diluted	$ 2.16	$ 1.88	$ 7.14	$ 5.04
Weighted average common shares outstanding
Basic	16,292,312	16,300,720	16,315,996	16,300,250
Diluted	16,423,912	16,393,792	16,445,568	16,398,350
Cash dividends declared	$ 1.03	$ 1.02	$ 3.29	$ 3.26
Fiduciary and Trust [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 8,820,000	$ 7,335,000	$ 25,562,000	$ 21,241,000
Deposit Account [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	2,389,000	2,118,000	6,475,000	6,322,000
Bank Servicing [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 6,668,000	$ 13,047,000	$ 23,444,000	$ 25,571,000