Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
INTEREST INCOME
Loans, including fees	$ 291,519	$ 263,093	$ 222,022
Securities:
Taxable	13,308	8,808	7,171
Tax-exempt	458	609	737
Federal funds sold	4	291	61
Interest-bearing deposits with banks	31,368	30,403	18,077
Total interest income	336,657	303,204	248,068
INTEREST EXPENSE
Deposits	52,738	40,462	18,790
Short-term borrowings	32	95	17
Junior subordinated debentures	1,966	2,171	2,122
Total interest expense	54,736	42,728	20,929
Net interest income	281,921	260,476	227,139
Provision for loan losses	8,287	3,802	8,512
Net interest income after provision for loan losses	273,634	256,674	218,627
NONINTEREST INCOME
Securities transactions (includes accumulated other comprehensive income reclassifications of $0, $9 and $(17), respectively)	812	47	4,060
Income from sales of loans	3,619	2,902	2,921
Insurance commissions	20,296	18,926	16,811
Cash management	16,866	13,123	11,155
(Loss)/gain on sale of other assets	(39)	575	(60)
Other	5,495	5,950	5,629
Total noninterest income	137,229	125,199	118,070
NONINTEREST EXPENSE
Salaries and employee benefits	153,024	139,547	125,149
Occupancy, net	12,704	13,491	12,591
Depreciation	12,623	10,537	9,603
Amortization of intangible assets	3,366	3,009	2,188
Data processing services	5,843	4,956	4,654
Net (income) expense from other real estate owned	(785)	239	421
Marketing and business promotion	8,554	8,028	7,389
Deposit insurance	1,143	2,427	2,261
Other	44,829	39,887	36,136
Total noninterest expense	241,301	222,121	200,392
Income before taxes	169,562	159,752	136,305
Income tax expense	34,683	33,938	49,866
Net income	$ 134,879	$ 125,814	$ 86,439
NET INCOME PER COMMON SHARE
Basic	$ 4.13	$ 3.85	$ 2.72
Diluted	$ 4.05	$ 3.76	$ 2.65
OTHER COMPREHENSIVE GAIN/(LOSS)
Unrealized gains/(losses) on securities, net of tax of $(1,918), $139 and $861, respectively	$ 5,593	$ (423)	$ (2,431)
Reclassification adjustment for (gains)/losses included in net income, net of tax of $0, $2 and $(7), respectively		(7)	10
Other comprehensive gain/(loss), net of tax of $(1,918), $141 and $854, respectively	5,593	(430)	(2,421)
Comprehensive income	140,472	125,384	84,018
Trust Revenue [Member]
NONINTEREST INCOME
Revenue	13,599	12,829	12,002
Service Charges on Deposits [Member]
NONINTEREST INCOME
Revenue	$ 76,581	$ 70,847	$ 65,552