Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest Income
Interest and fees on loans	$ 552,821	$ 537,301	$ 581,696
Interest and dividends on investment securities:
Taxable	62,458	57,392	68,698
Tax-exempt	14,683	14,426	13,157
Dividends	6,272	6,240	7,107
Interest on federal funds sold and other short-term investments	369	738	535
Total interest income	636,603	616,097	671,193
Interest Expense
Savings, NOW and money market	19,671	17,863	20,090
Time	27,882	29,928	37,466
Interest on short-term borrowings	972	590	1,387
Interest on long-term borrowings and junior subordinated debentures	113,321	119,996	122,369
Total interest expense	161,846	168,377	181,312
Net Interest Income	474,757	447,720	489,881
Provision for credit losses	1,884	16,095	25,552
Net Interest Income After Provision for Credit Losses	472,873	431,625	464,329
Non-Interest Income
Trust and investment services	9,512	8,610	7,690
Insurance commissions	16,853	15,907	15,494
Service charges on deposit accounts	22,771	24,115	24,752
Gains on securities transactions, net	745	14,678	2,587
Other-than-temporary impairment losses on securities	0	0	0
Portion recognized in other comprehensive income (before taxes)	0	0	(5,247)
Net impairment losses on securities recognized in earnings	0	0	(5,247)
Trading (losses) gains, net	(31)	909	2,793
Fees from loan servicing	7,013	7,020	4,843
Gains on sales of loans, net	1,731	33,695	46,998
Gains (losses) on sales of assets, net	18,087	10,947	(329)
Bank owned life insurance	6,392	5,962	6,855
Change in FDIC loss-share receivable	(20,792)	(8,427)	(7,459)
Other	15,335	15,237	21,969
Total non-interest income	77,616	128,653	120,946
Non-Interest Expense
Salary and employee benefits expense	193,489	194,410	199,968
Net occupancy and equipment expense	74,492	71,634	71,245
FDIC insurance assessment	14,051	16,767	14,292
Amortization of other intangible assets	9,919	8,258	9,783
Professional and legal fees	16,859	16,491	15,005
Loss on extinguishment of debt	10,132	0	0
Amortization of tax credit investments	24,196	14,352	4,157
Advertising	4,666	6,127	7,103
Other	55,451	53,299	53,347
Total non-interest expense	403,255	381,338	374,900
Income before income taxes	147,234	178,940	210,375
Income tax expense	31,062	46,979	66,748
Net Income	$ 116,172	$ 131,961	$ 143,627
Earnings Per Common Share:
Basic (in usd per share)	$ 0.56	$ 0.66	$ 0.73
Diluted (in usd per share)	$ 0.56	$ 0.66	$ 0.73
Cash Dividends Declared Per Common Share (in usd per share)	$ 0.444	$ 0.60	$ 0.65
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	205,716,293	199,309,425	197,354,159
Diluted (in shares)	205,716,293	199,309,425	197,354,372