Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest income:
Loans, including fees	$ 877,875	$ 772,030	$ 625,023
Loans held for sale	946	851	1,022
Securities-taxable	124,720	102,013	91,099
Securities-tax exempt	21,951	22,235	13,222
Short-term investments	2,776	3,452	1,801
Total interest income	1,028,268	900,581	732,167
Interest expense:
Deposits	130,715	76,546	48,934
Short-term borrowings	36,096	15,735	4,065
Long-term debt	12,619	15,988	20,052
Total interest expense	179,430	108,269	73,051
Net interest income	848,838	792,312	659,116
Provision for loan losses	36,116	58,968	110,659
Net interest income after provision for loan losses	812,722	733,344	548,457
Noninterest income:
Service charges on deposit accounts	85,272	83,166	74,187
Trust fees	55,488	44,538	46,589
Bank card and ATM fees	60,440	53,779	47,427
Investment and annuity fees and insurance commissions	25,348	23,741	22,978
Secondary mortgage market operations	15,632	15,209	16,282
Amortization of loss share receivable		(2,427)	(5,918)
Net gain on sales of assets	24,654	7,478	7,814
Securities transactions	(25,480)		1,754
Other income	43,786	42,297	39,668
Total noninterest income	285,140	267,781	250,781
Noninterest expense:
Compensation expense	330,968	320,096	287,783
Employee benefits	73,727	71,817	66,830
Personnel expense	404,695	391,913	354,613
Net occupancy expense	47,795	47,869	41,296
Equipment expense	16,367	14,841	13,663
Data processing expense	74,129	66,385	58,619
Professional services expense	41,579	40,235	29,561
Amortization of intangibles	22,050	22,417	19,781
Deposit insurance and regulatory fees	31,423	29,627	23,499
Other real estate income	(2,985)	(2,669)	(3,481)
Other expense	80,693	82,073	74,764
Total noninterest expense	715,746	692,691	612,315
Income before income taxes	382,116	308,434	186,923
Income taxes	58,346	92,802	37,627
Net income	$ 323,770	$ 215,632	$ 149,296
Earnings per common share-basic	$ 3.72	$ 2.49	$ 1.87
Earnings per common share-diluted	3.72	2.48	1.87
Dividends paid per share	$ 1.02	$ 0.96	$ 0.96
Weighted average shares outstanding-basic	85,355	84,695	77,850
Weighted average shares outstanding-diluted	85,521	84,963	77,949