Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
INTEREST INCOME
Interest and fees on loans	$ 615,627	$ 598,582	$ 587,526
Interest and dividends on investment securities:
Taxable	100,292	102,464	88,919
Tax exempt	31,152	29,064	27,345
Other interest	6,591	6,635	5,193
Total interest income	753,662	736,745	708,983
INTEREST EXPENSE
Interest on deposits	33,125	26,294	31,267
Interest on Federal funds purchased and securities sold under agreements to repurchase	943	1,219	1,322
Interest on other short-term funding	465	785	1,519
Interest on long-term funding	42,851	27,480	29,332
Total interest expense	77,384	55,778	63,440
NET INTEREST INCOME	676,278	680,967	645,543
Provision for credit losses	37,500	16,000	10,100
Net interest income after provision for credit losses	638,778	664,967	635,443
NONINTEREST INCOME
Trust service fees	48,840	48,403	45,633
Service charges on deposit accounts	65,471	68,779	70,009
Card-based and other nondeposit fees	51,325	49,512	49,913
Insurance commissions	75,363	44,421	44,024
Brokerage and annuity commissions	15,378	16,089	14,877
Total core fee-based revenue	256,377	227,204	224,456
Mortgage banking, net	32,263	21,320	48,847
Capital market fees, net	10,752	9,973	13,080
Bank owned life insurance income	9,796	13,576	11,855
Asset gains, net	1,592	10,288	5,413
Investment securities gains, net	8,133	494	564
Other	9,496	7,464	8,884
Total noninterest income	328,409	290,319	313,099
NONINTEREST EXPENSE
Personnel expense	404,741	390,399	397,015
Occupancy	60,896	57,677	59,409
Equipment	23,209	24,784	25,351
Technology	60,613	55,472	49,445
Business development and advertising	25,772	26,144	23,346
Other intangible amortization	3,094	3,747	4,043
Loan expense	14,102	13,866	13,162
Legal and professional fees	17,052	17,485	20,226
Foreclosure / OREO expense	4,494	6,722	10,068
FDIC expense	26,000	23,761	19,461
Other	57,426	59,184	59,123
Total noninterest expense	697,399	679,241	680,649
Income before income taxes	269,788	276,045	267,893
Income tax expense	81,487	85,536	79,201
Net income	188,301	190,509	188,692
Preferred stock dividends	7,155	5,002	5,158
Net income available to common equity	$ 181,146	$ 185,507	$ 183,534
Earnings per common share:
Basic (in usd per share)	$ 1.20	$ 1.17	$ 1.10
Diluted (in usd per share)	$ 1.19	$ 1.16	$ 1.10
Average common shares outstanding:
Basic (in shares)	149,350	157,286	165,584
Diluted (in shares)	150,603	158,254	165,802