Fair Value Measurements (Estimated Fair Values Of Financial Instruments) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 2,752,176	$ 2,907,592	$ 4,487,361
Securities held to maturity	364,997	365,996	366,267
Loans, net	8,705,639	7,884,982	7,974,144
Deposits	18,245,197	16,756,748	16,063,873
Federal funds purchased and repurchase agreements	601,204	722,202	658,246
Junior subordinated deferrable interest debentures	123,712	123,712	123,712
Subordinated notes payable and other borrowings	100,012	100,026	100,031
Carrying Amount [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2,752,176	2,907,592
Securities held to maturity	364,997	365,996
Cash surrender value of life insurance policies	137,009	133,967
Accrued interest receivable	63,216	78,869
Deposits	18,245,197	16,756,748
Federal funds purchased and repurchase agreements	601,204	722,202
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes payable and other borrowings	100,012	100,026
Accrued interest payable	1,882	4,431
Carrying Amount [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	8,705,639	7,884,982
Estimated Fair Value [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2,752,176	2,907,592
Securities held to maturity	409,258	404,461
Cash surrender value of life insurance policies	137,009	133,967
Accrued interest receivable	63,216	78,869
Deposits	18,245,906	16,757,708
Federal funds purchased and repurchase agreements	601,204	722,202
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes payable and other borrowings	89,506	100,101
Accrued interest payable	1,882	4,431
Estimated Fair Value [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 8,812,390	$ 7,951,742

The sum of cash and cash equivalents plus Federal Funds Sold. Cash and cash equivalents consist of short term, highly liquid investments that are readily convertible to known amounts of cash and are so near their maturity that they present negligible risk of changes in value due to changes in interest rates -- usually with an original maturity less than 90 days.

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