Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
INTEREST INCOME
Loans, including fees	$ 311,987	$ 291,519	$ 263,093
Debt securities:
Taxable	8,591	13,308	8,808
Tax-exempt	487	458	609
Federal funds sold		4	291
Interest-bearing deposits with banks	6,049	31,368	30,403
Total interest income	327,114	336,657	303,204
INTEREST EXPENSE
Deposits	18,472	52,738	40,462
Short-term borrowings	8	32	95
Junior subordinated debentures	1,966	1,966	2,171
Total interest expense	20,446	54,736	42,728
Net interest income	306,668	281,921	260,476
Provision for credit losses	62,648	8,287	3,802
Net interest income after provision for credit losses	244,020	273,634	256,674
NONINTEREST INCOME
Securities transactions (includes accumulated other comprehensive income reclassifications of $0, $0 and $9, respectively)	(389)	812	47
Income from sales of loans	6,067	3,619	2,902
Insurance commissions	20,996	20,296	18,926
Cash management	15,411	16,866	13,123
Gain/(loss) on sale of other assets	130	(39)	575
Other	7,439	5,495	5,950
Total noninterest income	137,222	137,229	125,199
NONINTEREST EXPENSE
Salaries and employee benefits	164,727	153,024	139,547
Occupancy, net	16,421	12,704	13,491
Depreciation	14,609	12,623	10,537
Amortization of intangible assets	3,815	3,366	3,009
Data processing services	6,753	5,843	4,956
Net (income)/expense from other real estate owned	(1,531)	(785)	239
Marketing and business promotion	6,996	8,554	8,028
Deposit insurance	2,081	1,143	2,427
Other	43,859	44,829	39,887
Total noninterest expense	257,730	241,301	222,121
Income before taxes	123,512	169,562	159,752
Income tax expense	23,926	34,683	33,938
Net income	$ 99,586	$ 134,879	$ 125,814
NET INCOME PER COMMON SHARE
Basic	$ 3.05	$ 4.13	$ 3.85
Diluted	$ 3.00	$ 4.05	$ 3.76
OTHER COMPREHENSIVE GAIN/(LOSS)
Unrealized gains/(losses) on securities, net of tax of $(1,326), $(1,918) and $139, respectively	$ 3,976	$ 5,593	$ (423)
Reclassification adjustment for gains included in net income, net of tax of $0, $0 and $2, respectively			(7)
Other comprehensive gain/(loss), net of tax of $(1,326), $(1,918) and $141, respectively	3,976	5,593	(430)
Comprehensive income	103,562	140,472	125,384
Trust Revenue [Member]
NONINTEREST INCOME
Revenue	13,130	13,599	12,829
Service Charges on Deposits [Member]
NONINTEREST INCOME
Revenue	$ 74,438	$ 76,581	$ 70,847