Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest income:
Loans, including fees	$ 583,751	$ 601,466	$ 629,882
Loans held for sale	678	708	882
Securities-taxable	90,522	85,806	85,426
Securities-tax exempt	3,447	3,873	4,621
Short-term investments	1,248	960	1,399
Total interest income	679,646	692,813	722,210
Interest expense:
Deposits	33,876	23,223	24,175
Short-term borrowings	1,078	2,361	4,542
Long-term debt	19,518	12,535	12,762
Total interest expense	54,472	38,119	41,479
Net interest income	625,174	654,694	680,731
Provision for loan losses	73,038	33,840	32,734
Net interest income after provision for loan losses	552,136	620,854	647,997
Noninterest income:
Service charges on deposit accounts	72,813	77,006	79,000
Trust fees	45,627	44,826	38,186
Bank card and ATM fees	46,480	45,031	45,939
Investment and annuity fees	20,669	20,291	19,574
Secondary mortgage market operations	12,579	8,036	12,543
Insurance commissions and fees	8,567	9,473	15,804
Amortization of loss share receivable	(5,747)	(12,102)	(2,239)
Other income	35,961	35,438	37,231
Securities transactions	335		105
Total noninterest income	237,284	227,999	246,143
Noninterest expense:
Compensation expense	278,661	276,881	291,225
Employee benefits	54,880	51,415	65,257
Personnel expense	333,541	328,296	356,482
Net occupancy expense	44,842	43,596	48,854
Equipment expense	15,494	16,953	20,026
Data processing expense	55,590	51,369	48,367
Professional services expense	40,198	33,221	39,357
Amortization of intangibles	24,184	26,797	29,470
Telecommunications and postage	14,127	14,676	17,432
Deposit insurance and regulatory fees	16,736	11,872	14,914
Other real estate expense, net	2,740	2,758	8,036
Other expense	72,203	77,128	95,336
Total noninterest expense	619,655	606,666	678,274
Income before income taxes	169,765	242,187	215,866
Income taxes	38,304	66,465	52,510
Net income	$ 131,461	$ 175,722	$ 163,356
Earnings per common share-basic	$ 1.64	$ 2.10	$ 1.93
Earnings per common share-diluted	$ 1.64	$ 2.10	$ 1.93