Consolidated Condensed Statements Of Income - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Interest and dividend income:
Interest and fees on loans	$ 77,787,000	$ 81,176,000	$ 150,203,000	$ 159,913,000
Interest and dividends on:
Obligations of U.S. Government, its agencies and other securities	7,624,000	4,600,000	13,754,000	8,856,000
Interest Income, Securities, State and Municipal	2,676,000	2,032,000	5,123,000	4,069,000
Other interest income	260,000	186,000	413,000	329,000
Total interest and dividend income	88,347,000	87,994,000	169,493,000	173,167,000
Interest on deposits:
Demand and savings deposits	1,333,000	401,000	1,684,000	787,000
Time deposits	708,000	1,285,000	1,428,000	2,869,000
Interest on borrowings:
Short-term borrowings	190,000	182,000	434,000	365,000
Long-term debt	2,177,000	2,275,000	4,322,000	4,561,000
Total interest expense	4,408,000	4,143,000	7,868,000	8,582,000
Net interest income	83,939,000	83,851,000	161,625,000	164,585,000
Recovery of credit losses	2,991,000	(4,040,000)	(1,614,000)	(8,895,000)
Net interest income after provision for credit losses	80,948,000	87,891,000	163,239,000	173,480,000
Noninterest Income [Abstract]
Debit card fee income	6,731,000	6,758,000	12,857,000	12,844,000
Bank owned life insurance income	2,374,000	1,149,000	3,549,000	2,314,000
ATM Fees	583,000	655,000	1,115,000	1,185,000
Gain on equity securities, net	709,000	467,000	3,062,000	2,277,000
Other components of net periodic benefit income	3,027,000	2,038,000	6,054,000	4,076,000
Other	1,407,000	2,411,000	4,160,000	5,027,000
Total other income	31,193,000	31,238,000	62,849,000	65,327,000
Other expense:
Salaries and employee benefits	31,052,000	30,303,000	61,573,000	60,199,000
Employee Benefits and Share-based Compensation	10,199,000	10,056,000	20,698,000	20,257,000
Occupancy expense	3,040,000	3,027,000	6,254,000	6,667,000
Furniture and equipment expense	2,934,000	2,756,000	5,871,000	5,366,000
Data processing fees	8,416,000	7,150,000	15,920,000	14,862,000
Professional fees and services	6,775,000	6,973,000	12,633,000	12,637,000
Marketing	1,019,000	1,290,000	2,336,000	2,781,000
Insurance	1,245,000	1,276,000	2,650,000	2,967,000
Communication	935,000	770,000	1,825,000	1,892,000
Excise and Sales Taxes	1,167,000	1,103,000	2,359,000	2,211,000
Amortization of Intangible Assets	403,000	479,000	805,000	958,000
Foundation contribution expense	0	4,000,000	0	4,000,000
Other expense	2,863,000	2,217,000	4,497,000	4,468,000
Total other expense	70,048,000	71,400,000	137,421,000	139,265,000
Income before income taxes	42,093,000	47,729,000	88,667,000	99,542,000
Income taxes	7,769,000	8,597,000	15,468,000	17,579,000
Net income	$ 34,324,000	$ 39,132,000	$ 73,199,000	$ 81,963,000
Net income available to common shareholders
Basic	$ 2.11	$ 2.39	$ 4.51	$ 5.02
Diluted	$ 2.10	$ 2.38	$ 4.48	$ 4.98
Weighted average common shares outstanding
Basic	16,249,307	16,340,690	16,234,598	16,327,838
Diluted	16,361,246	16,472,800	16,346,141	16,455,673
Quarterly Dividend
Weighted average common shares outstanding
Cash dividends declared	$ 1.04	$ 1.03	$ 2.08	$ 2.06
Special Dividend
Weighted average common shares outstanding
Cash dividends declared	$ 0	$ 0	$ 0	$ 200
Fiduciary and Trust [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 8,859,000	$ 8,569,000	$ 17,656,000	$ 16,742,000
Deposit Account [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	2,563,000	2,032,000	4,637,000	4,086,000
Bank Servicing [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 4,940,000	$ 7,159,000	$ 9,759,000	$ 16,776,000