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	$ 944,233	$ 877,384	$ 862,916
Investment securities available for sale	67,467	59,154	57,832
Trading account assets	91	303	456
Mortgage loans held for sale	2,646	2,546	2,304
Federal Reserve Bank balances	4,356	3,144	2,081
Other earning assets	4,010	3,431	3,103
Total interest income	1,022,803	945,962	928,692
Interest expense:
Deposits	64,206	65,534	55,179
Federal funds purchased and securities sold under repurchase agreements	200	168	220
Long-term debt	59,217	52,942	54,009
Total interest expense	123,623	118,644	109,408
Net interest income	899,180	827,318	819,284
Provision for loan losses	28,000	19,010	33,831
Net interest income after provision for loan losses	871,180	808,308	785,453
Non-interest income:
Service charges on deposit accounts	81,425	80,142	78,897
Fiduciary and asset management fees	46,594	45,928	45,226
Brokerage revenue	27,028	27,855	27,088
Mortgage banking income	24,259	24,096	18,354
Bankcard fees	33,318	33,172	32,931
Investment securities gains, net	6,011	2,769	1,331
Other fee income	20,220	21,170	19,130
Gain on sale of Memphis branches, net	0	0	5,789
Other non-interest income	34,339	32,788	33,358
Total non-interest income	273,194	267,920	262,104
Non-interest expense:
Salaries and other personnel expense	402,026	380,918	371,904
Net occupancy and equipment expense	109,347	107,466	105,806
Third-party processing expense	46,320	42,851	40,042
FDIC insurance and other regulatory fees	26,714	27,091	33,485
Professional fees	26,698	26,646	26,440
Advertising expense	20,264	15,477	24,037
Foreclosed real estate expense, net	12,838	22,803	25,321
Fair value adjustment to Visa derivative	5,795	1,464	3,041
Loss on early extinguishment of debt, net	4,735	1,533	0
Merger-related expense	1,636	0	0
Restructuring charges	8,267	36	20,585
Other operating expenses	91,283	91,370	94,337
Total non-interest expense	755,923	717,655	744,998
Income before income taxes	388,451	358,573	302,559
Income tax expense	(141,667)	(132,491)	(107,310)
Net income	246,784	226,082	195,249
Dividends on preferred stock	10,238	10,238	10,238
Net income available to common shareholders	$ 236,546	$ 215,844	$ 185,011
Net income per common share, basic (per share)	$ 1.90	$ 1.63	$ 1.34
Net income per common share, diluted (per share)	$ 1.89	$ 1.62	$ 1.33
Weighted average common shares outstanding, basic	124,389	132,423	138,495
Weighted average common shares outstanding, diluted	125,078	133,201	139,154