Consolidated Condensed Statements Of Income - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest and dividend income:
Interest and fees on loans	$ 82,617,000	$ 84,213,000	$ 243,459,000	$ 238,687,000
Interest and dividends on:
Obligations of U.S. Government, its agencies and other securities	4,841,000	6,326,000	15,398,000	20,240,000
Interest Income, Securities, State and Municipal	2,045,000	2,225,000	6,396,000	6,750,000
Other interest income	63,000	1,825,000	667,000	2,994,000
Total interest and dividend income	89,566,000	94,589,000	265,920,000	268,671,000
Interest on deposits:
Demand and savings deposits	803,000	9,649,000	8,652,000	25,553,000
Time deposits	2,662,000	4,694,000	10,293,000	12,828,000
Interest on borrowings:
Short-term borrowings	217,000	478,000	912,000	1,977,000
Long-term debt	2,044,000	2,667,000	4,754,000	7,585,000
Total interest expense	5,726,000	17,488,000	24,611,000	47,943,000
Net interest income	83,840,000	77,101,000	241,309,000	220,728,000
Provision for loan losses	13,836,000	1,967,000	31,213,000	6,384,000
Net interest income after provision for loan losses	70,004,000	75,134,000	210,096,000	214,344,000
Noninterest Income [Abstract]
Debit card fee income	5,853,000	5,313,000	16,373,000	14,909,000
Bank owned life insurance income	1,192,000	1,107,000	3,619,000	3,399,000
ATM Fees	491,000	482,000	1,341,000	1,382,000
Gains (Losses) on Sales of Other Real Estate	569,000	(53,000)	1,214,000	(224,000)
Debt Securities, Available-for-sale, Realized Gain (Loss)	(27,000)	186,000	3,286,000	(421,000)
Loss (gain) on equity securities, net	1,201,000	3,335,000	(749,000)	5,309,000
Other components of net periodic benefit income	1,988,000	1,183,000	5,964,000	3,549,000
Other	2,791,000	2,617,000	5,826,000	5,370,000
Total other income	36,558,000	28,136,000	90,008,000	72,969,000
Other expense:
Salaries and employee benefits	31,632,000	30,713,000	90,760,000	88,611,000
Employee Benefits and Share-based Compensation	10,676,000	10,389,000	29,799,000	27,833,000
Occupancy expense	3,835,000	3,226,000	10,571,000	9,460,000
Furniture and equipment expense	4,687,000	4,177,000	13,856,000	12,713,000
Data processing fees	3,275,000	2,935,000	8,344,000	7,973,000
Professional fees and services	7,977,000	6,702,000	21,944,000	22,814,000
Marketing	1,454,000	1,604,000	4,076,000	4,285,000
Insurance	1,541,000	276,000	4,568,000	2,813,000
Communication	958,000	1,387,000	2,987,000	4,095,000
Excise and Sales Taxes	1,125,000	746,000	3,386,000	2,805,000
Amortization of Intangible Assets	525,000	741,000	1,738,000	1,732,000
Other expense	2,174,000	2,842,000	8,905,000	7,623,000
Total other expense	69,859,000	65,738,000	200,934,000	192,757,000
Income before income taxes	36,703,000	37,532,000	99,170,000	94,556,000
Income taxes	5,857,000	6,386,000	16,447,000	15,792,000
Net income	$ 30,846,000	$ 31,146,000	$ 82,723,000	$ 78,764,000
Net income available to common shareholders
Basic	$ 1.89	$ 1.90	$ 5.07	$ 4.86
Diluted	$ 1.88	$ 1.89	$ 5.04	$ 4.84
Weighted average common shares outstanding
Basic	16,300,720	16,382,798	16,300,250	16,198,294
Diluted	16,393,792	16,475,741	16,398,350	16,287,695
Cash dividends declared	$ 1.02	$ 1.01	$ 3.26	$ 3.23
Fiduciary and Trust [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 7,335,000	$ 6,842,000	$ 21,241,000	$ 20,500,000
Deposit Account [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	2,118,000	2,864,000	6,322,000	8,078,000
Bank Servicing [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 13,047,000	$ 4,260,000	$ 25,571,000	$ 11,118,000