Notional Amount of Off-Balance Sheet Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Commitments to extend credit for loans (excluding credit card loans)
Commitments and Contingencies Disclosure [Line Items]
Notional Amount of off-balance sheet financial instruments	$ 2,403,773	$ 2,202,838
Commitments to extend credit under credit card loans
Commitments and Contingencies Disclosure [Line Items]
Notional Amount of off-balance sheet financial instruments	2,145,793	2,059,193
Commercial letters of credit
Commitments and Contingencies Disclosure [Line Items]
Notional Amount of off-balance sheet financial instruments	2,228	19,564
Standby letters of credit
Commitments and Contingencies Disclosure [Line Items]
Notional Amount of off-balance sheet financial instruments	321,084	320,119
Futures contracts
Commitments and Contingencies Disclosure [Line Items]
Notional Amount of off-balance sheet financial instruments	3,500	30,600
Forward foreign exchange contracts
Commitments and Contingencies Disclosure [Line Items]
Notional Amount of off-balance sheet financial instruments	28,857	119,200
Spot foreign exchange contracts
Commitments and Contingencies Disclosure [Line Items]
Notional Amount of off-balance sheet financial instruments	$ 3,001	$ 3,040