Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest income:
Loans, including fees	$ 625,023	$ 583,751	$ 601,466
Loans held for sale	1,022	678	708
Securities-taxable	91,099	90,522	85,806
Securities-tax exempt	13,222	3,447	3,873
Short-term investments	1,801	1,248	960
Total interest income	732,167	679,646	692,813
Interest expense:
Deposits	48,934	33,876	23,223
Short-term borrowings	4,065	1,078	2,361
Long-term debt	20,052	19,518	12,535
Total interest expense	73,051	54,472	38,119
Net interest income	659,116	625,174	654,694
Provision for loan losses	110,659	73,038	33,840
Net interest income after provision for loan losses	548,457	552,136	620,854
Noninterest income:
Service charges on deposit accounts	74,187	72,813	77,006
Trust fees	46,589	45,627	44,826
Bank card and ATM fees	47,427	46,480	45,031
Investment and annuity fees	18,477	20,669	20,291
Secondary mortgage market operations	16,282	12,579	8,036
Insurance commissions and fees	4,501	8,567	9,473
Amortization of loss share receivable	(5,918)	(5,747)	(12,102)
Other income	47,482	35,961	35,438
Securities transactions	1,754	335
Total noninterest income	250,781	237,284	227,999
Noninterest expense:
Compensation expense	287,783	278,661	276,881
Employee benefits	55,884	54,880	51,415
Personnel expense	343,667	333,541	328,296
Net occupancy expense	41,296	44,842	43,596
Equipment expense	13,663	15,494	16,953
Data processing expense	58,619	55,590	51,369
Professional services expense	29,561	40,198	33,221
Amortization of intangibles	19,781	24,184	26,797
Telecommunications and postage	13,146	14,127	14,676
Deposit insurance and regulatory fees	23,499	16,736	11,872
Other real estate expense, net	(3,481)	2,740	2,758
Other expense	72,564	72,203	77,128
Total noninterest expense	612,315	619,655	606,666
Income before income taxes	186,923	169,765	242,187
Income taxes	37,627	38,304	66,465
Net income	$ 149,296	$ 131,461	$ 175,722
Earnings per common share-basic	$ 1.87	$ 1.64	$ 2.10
Earnings per common share-diluted	1.87	1.64	2.10
Dividends paid per share	$ 0.96	$ 0.96	$ 0.96
Weighted average shares outstanding-basic	77,850	78,197	81,804
Weighted average shares outstanding-diluted	77,949	78,307	82,034