CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Interest and fees on loans	$ 308,210	$ 286,165	$ 253,949
Interest and dividends on taxable investments	65,904	63,504	60,159
Interest and dividends on nontaxable investments	11,613	13,064	15,347
Total interest income	385,727	362,733	329,455
Interest expense:
Interest on deposits	20,460	10,658	8,031
Interest on borrowings	1,848	2,343	1,845
Interest on subordinated notes payable	346	0	0
Interest on subordinated debt held by unconsolidated subsidiary trusts	3,898	4,677	3,904
Total interest expense	26,552	17,678	13,780
Net interest income	359,175	345,055	315,675
Provision for loan losses	8,430	10,837	10,984
Net interest income after provision for loan losses	350,745	334,218	304,691
Noninterest revenues:
Deposit service fees	65,602	70,384	67,896
Other banking services	4,881	4,968	5,466
Employee benefit services	97,167	92,279	80,830
Insurance services	32,199	30,317	26,150
Wealth management services	25,869	25,772	22,079
Unrealized gain on equity securities	19	657	0
Loss on debt extinguishment	0	(318)	0
Gain on sales of investment securities, net	4,882	0	2
Total noninterest revenues	230,619	224,059	202,423
Noninterest expenses:
Salaries and employee benefits	219,916	207,363	186,903
Occupancy and equipment	39,850	39,948	35,561
Data processing and communications	41,407	39,094	37,579
Amortization of intangible assets	15,956	18,155	16,941
Legal and professional fees	10,783	10,644	11,576
Business development and marketing	11,416	9,383	9,994
Acquisition expenses	8,608	(769)	25,986
Other expenses	24,090	21,471	22,609
Total noninterest expenses	372,026	345,289	347,149
Income before income taxes	209,338	212,988	159,965
Income taxes	40,275	44,347	9,248
Net income	$ 169,063	$ 168,641	$ 150,717
Basic earnings per share (in dollars per share)	$ 3.26	$ 3.28	$ 3.07
Diluted earnings per share (in dollars per share)	$ 3.23	$ 3.24	$ 3.03