Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Assets:
Cash and due from banks	$ 623,204	$ 574,039	$ 587,655
Interest-bearing deposits	1,497,478	2,314,251	2,101,014
Federal funds sold and resell agreements	8,052	19,302	10,002
Total cash and cash equivalents	2,128,734	2,907,592	2,698,671
Securities held to maturity, at amortized cost	365,603	365,996	341,034
Securities available for sale, at estimated fair value	8,568,215	7,789,700	5,662,211
Trading account securities	16,846	13,609	20,746
Loans, net of unearned discounts	8,126,713	7,995,129	8,025,080
Less: Allowance for loan losses	(107,181)	(110,147)	(124,321)
Net loans	8,019,532	7,884,982	7,900,759
Premises and equipment, net	321,681	319,042	313,233
Goodwill	535,560	528,072	527,684
Other intangible assets, net	11,033	10,604	13,215
Cash surrender value of life insurance policies	135,035	133,967	130,910
Accrued interest receivable and other assets	314,942	363,681	333,181
Total assets	20,417,181	20,317,245	17,941,644
Liabilities:
Non-interest-bearing demand deposits	6,784,112	6,672,555	5,413,002
Interest-bearing deposits	10,124,909	10,084,193	9,296,557
Total deposits	16,909,021	16,756,748	14,709,559
Federal funds purchased and repurchase agreements	637,098	722,202	553,571
Junior subordinated deferrable interest debentures	123,712	123,712	123,712
Other long-term borrowings	100,022	100,026	250,040
Accrued interest payable and other liabilities	326,615	331,020	207,411
Total liabilities	18,096,468	18,033,708	15,844,293
Shareholders' Equity:
Preferred stock, par value $0.01 per share; 10,000,000 shares authorized; none issued
Common stock, par value $0.01 per share; 210,000,000 shares authorized; 61,372,763, shares issued at March 31, 2012, 61,271,603 shares issued at December 31, 2011 and 61,244,157 shares issued at March 31, 2011	614	613	613
Additional paid-in capital	688,150	680,803	668,237
Retained earnings	1,387,553	1,354,759	1,273,826
Accumulated other comprehensive income, net of tax	244,396	247,734	154,818
Treasury stock, 7,640 shares at December 31, 2011 and 2,464 shares at March 31, 2011, at cost		(372)	(143)
Total shareholders' equity	2,320,713	2,283,537	2,097,351
Total liabilities and shareholders' equity	$ 20,417,181	$ 20,317,245	$ 17,941,644