Notional Amount of Off-Balance Sheet Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Commitments to extend credit for loans (excluding credit card loans) [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	$ 6,406,215	$ 6,671,794
Commitments to extend credit under credit card loans [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	2,729,837	2,986,581
Commercial letters of credit [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	6,024	11,541
Standby letters of credit [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	382,448	360,468
Futures contracts [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	1,300
Forward foreign exchange contracts [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	64,536	75,611
Spot foreign exchange contracts [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	$ 6,350	$ 10,391