Fair Value Measurements (Estimated Fair Values Of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 2,128,734	$ 2,907,592	$ 2,698,671
Securities held to maturity	365,603	365,996	341,034
Loans, net	8,019,532	7,884,982	7,900,759
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
Subordinated notes payable and other borrowings	100,022	100,026	250,040
Level 2 Inputs [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2,128,734	2,907,592
Securities held to maturity	365,603	365,996
Cash surrender value of life insurance policies	135,035	133,967
Accrued interest receivable	61,833	78,869
Deposits	16,909,021	16,756,748
Federal funds purchased and repurchase agreements	637,098	722,202
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes payable and other borrowings	100,022	100,026
Accrued interest payable	2,212	4,431
Level 2 Inputs [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2,128,734	2,907,592
Securities held to maturity	402,829	404,461
Cash surrender value of life insurance policies	135,035	133,967
Accrued interest receivable	61,833	78,869
Deposits	16,909,615	16,757,708
Federal funds purchased and repurchase agreements	637,098	722,202
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes payable and other borrowings	86,094	100,101
Accrued interest payable	2,212	4,431
Level 3 Inputs [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	8,019,532	7,884,982
Level 3 Inputs [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 8,119,248	$ 7,951,742