Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest and Dividend Income, Operating [Abstract]
Interest and Fee Income, Loans and Leases	$ 321,385	$ 271,145	$ 248,687
Interest and Dividend Income, Securities, by Classification [Abstract]
Interest Income, Securities, US Treasury and Other US Government	26,213	29,479	27,440
Interest Income, Securities, State and Municipal	8,955	8,770	7,210
Other Interest and Dividend Income	3,947	1,407	3,087
Interest and Dividend Income, Operating, Total	360,500	310,801	286,424
Interest Expense, Deposits [Abstract]
Interest Expense, NOW Accounts, Money Market Accounts, and Savings Deposits	33,348	19,815	9,464
Interest Expense, Time Deposits	17,494	12,375	9,629
Interest Expense, Borrowings [Abstract]
Interest Expense, Short-term Borrowings	2,476	1,600	992
Interest Expense, Long-term Debt	9,445	10,113	22,580
Total interest expense	62,763	43,903	42,665
Net interest income	297,737	266,898	243,759
Provision for loan losses	6,171	7,945	8,557
Interest Income (Expense), after Provision for Loan Loss, Total	291,566	258,953	235,202
Noninterest Income [Abstract]
Debit card fee income	20,250	17,317	15,798
Bank Owned Life Insurance Income	4,557	6,815	4,858
ATM Fees	1,828	1,978	2,253
OREO devaluations	225	491	458
Gains (Losses) on Sales of Other Real Estate	(222)	4,235	251
Gain (Loss) on Sale of Investments	(421)	(2,271)	1,821
Gain on equity securities, net	5,118	4,616	1,210
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	4,732	6,820	5,794
Gain (Loss) on Sales of Loans, Net	0	2,826	0
Noninterest Income, Other	7,473	7,236	5,352
Noninterest Income	97,193	101,101	86,429
Noninterest Expense [Abstract]
Salaries	119,514	103,755	92,177
Employee benefits	36,806	30,289	24,937
Occupancy expense	12,815	11,251	10,201
Furniture and equipment expense	17,032	16,139	15,324
Data processing fees	10,750	8,477	7,250
Professional fees and services	33,317	28,894	24,833
Marketing	5,753	5,144	4,374
Insurance	3,130	5,289	6,354
Communication	5,351	4,981	4,826
State tax expense	3,829	3,813	3,583
Amortization of Intangible Assets	2,355	578	0
Miscellaneous	13,336	10,145	9,303
Total other expense	263,988	228,755	203,162
Income before income taxes	124,771	131,299	118,469
Income taxes	22,071	20,912	34,227
Net Income (Loss) Attributable to Parent	$ 102,700	$ 110,387	$ 84,242
Earnings Per Share [Abstract]
Basic (in dollars per share)	$ 6.33	$ 7.13	$ 5.51
Diluted (in dollars per share)	$ 6.29	$ 7.07	$ 5.47
Fiduciary and Trust [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	$ 27,768	$ 26,293	$ 23,735
Deposit Account [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	10,835	11,461	12,653
Bank Servicing [Member]
Noninterest Income [Abstract]
Revenue from Contract with Customer, Including Assessed Tax	15,500	14,266	13,162
Noninterest Income, Other	$ 15,500	$ 14,300	$ 13,200