Summary of Derivative Activity and the Related Impact on Consolidated Statements of Income (Detail) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Interest rate swaps | Derivatives designated as hedging instruments | Interest rate risks | Interest expense-borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	$ 2,337	$ 5,943	$ 12,205	$ 18,531
Interest rate swaps | Derivatives designated as hedging instruments | Interest rate risks | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	(400)		(467)
Derivatives designated as hedging instruments | Interest rate risks
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	1,937	5,943	11,738	18,531
Derivatives not designated as hedging instruments | Currency exchange risks
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	(167)	(116)	(27)	103
Derivatives not designated as hedging instruments | Currency exchange risks | Foreign exchange forwards | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	3,591	(2,987)	540	178
Derivatives not designated as hedging instruments | Currency exchange risks | Loans | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	(3,758)	2,871	(567)	(75)
Derivatives not designated as hedging instruments | Other derivative instruments | Other derivatives | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	584	62	(743)	62
Derivatives not designated as hedging instruments | Other derivative instruments | Foreign exchange forwards | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	658	420	1,448	1,252
Derivatives not designated as hedging instruments | Other derivative instruments | Equity warrant assets | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	$ 5,518	$ 3,762	$ 23,375	$ 3,073