Summary of Derivative Activity and Related Impact on Consolidated Statements of Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Derivatives designated as hedging instruments | Interest rate risks
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	$ 14,016		$ 24,682		$ 20,797
Derivatives designated as hedging instruments | Interest rate risks | Interest rate swaps | Interest expense-borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	14,486		24,682		20,967
Derivatives designated as hedging instruments | Interest rate risks | Interest rate swaps | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	(470)				(170)
Derivatives not designated as hedging instruments | Currency exchange risks
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	152		283		(313)
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	(1,821)		(427)		1,945
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	1,973		710		(2,258)
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	2,259		1,914		1,730
Derivatives not designated as hedging instruments | Other derivative instruments | Equity Warrant Asset | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	37,439		6,556		(55)
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	$ (2,520)	[1]	$ 342	[1]

[1] Primarily represents the change in fair value of loan conversion options.