Consolidated Condensed Statements Of Income - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest and dividend income:
Interest and fees on loans	$ 80,155,000	$ 82,471,000	$ 160,842,000	$ 154,474,000
Interest and dividends on:
Obligations of U.S. Government, its agencies and other securities	5,026,000	6,919,000	10,557,000	13,914,000
Interest Income, Securities, State and Municipal	2,151,000	2,308,000	4,351,000	4,525,000
Other interest income	113,000	528,000	604,000	1,169,000
Total interest and dividend income	87,445,000	92,226,000	176,354,000	174,082,000
Interest on deposits:
Demand and savings deposits	1,507,000	8,811,000	7,849,000	15,904,000
Time deposits	3,346,000	4,357,000	7,631,000	8,134,000
Interest on borrowings:
Short-term borrowings	233,000	760,000	695,000	1,499,000
Long-term debt	1,173,000	2,447,000	2,710,000	4,918,000
Total interest expense	6,259,000	16,375,000	18,885,000	30,455,000
Net interest income	81,186,000	75,851,000	157,469,000	143,627,000
Provision for loan losses	12,224,000	1,919,000	17,377,000	4,417,000
Net interest income after provision for loan losses	68,962,000	73,932,000	140,092,000	139,210,000
Noninterest Income [Abstract]
Debit card fee income	5,560,000	5,227,000	10,520,000	9,596,000
Bank owned life insurance income	1,179,000	1,286,000	2,427,000	2,292,000
ATM Fees	438,000	460,000	850,000	900,000
Gains (Losses) on Sales of Other Real Estate	841,000	(159,000)	645,000	(171,000)
Debt Securities, Available-for-sale, Realized Gain (Loss)	3,313,000	(607,000)	3,313,000	(607,000)
Loss (gain) on equity securities, net	(977,000)	232,000	(1,950,000)	1,974,000
Other components of net periodic benefit income	1,988,000	1,183,000	3,976,000	2,366,000
Other	1,395,000	1,556,000	3,035,000	2,753,000
Total other income	30,964,000	22,808,000	53,450,000	44,833,000
Other expense:
Salaries and employee benefits	30,699,000	32,093,000	59,128,000	57,898,000
Employee Benefits and Share-based Compensation	9,080,000	9,014,000	19,123,000	17,444,000
Occupancy expense	3,256,000	3,223,000	6,736,000	6,234,000
Furniture and equipment expense	4,850,000	4,386,000	9,169,000	8,536,000
Data processing fees	2,577,000	2,905,000	5,069,000	5,038,000
Professional fees and services	6,901,000	10,106,000	13,967,000	16,112,000
Marketing	1,136,000	1,455,000	2,622,000	2,681,000
Insurance	1,477,000	1,381,000	3,027,000	2,537,000
Communication	874,000	1,375,000	2,029,000	2,708,000
Excise and Sales Taxes	1,116,000	1,054,000	2,261,000	2,059,000
Amortization of Intangible Assets	607,000	702,000	1,213,000	991,000
Other expense	2,226,000	2,498,000	6,731,000	4,781,000
Total other expense	64,799,000	70,192,000	131,075,000	127,019,000
Income before income taxes	35,127,000	26,548,000	62,467,000	57,024,000
Income taxes	5,622,000	4,385,000	10,590,000	9,406,000
Net income	$ 29,505,000	$ 22,163,000	$ 51,877,000	$ 47,618,000
Net income available to common shareholders
Basic	$ 1.81	$ 1.34	$ 3.18	$ 2.96
Diluted	$ 1.80	$ 1.33	$ 3.16	$ 2.94
Weighted average common shares outstanding
Basic	16,296,427	16,560,545	16,300,015	16,106,043
Diluted	16,375,434	16,642,571	16,400,657	16,193,643
Cash dividends declared	$ 1.02	$ 1.01	$ 2.24	$ 2.22
Fiduciary and Trust [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 6,793,000	$ 6,935,000	$ 13,906,000	$ 13,658,000
Deposit Account [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	1,676,000	2,655,000	4,204,000	5,214,000
Bank Servicing [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 8,758,000	$ 4,040,000	$ 12,524,000	$ 6,858,000