Commitments, Contingencies and Guarantees - Notional Amount of Off-Balance Sheet Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
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	$ 8,851,333	$ 7,409,338
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	3,472,339	3,188,905
Commercial letters of credit [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	3,160	4,460
Standby letters of credit [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	346,617	299,933
Forward contracts [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	51,273	58,287
Spot foreign exchange contracts [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract or notional amount of off-balance sheet financial instruments	$ 680	$ 1,980