Summary of Derivative Activity and Related Impact on Consolidated Statements of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
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	$ 1,696		$ 3,695		$ 3,925		$ 9,868
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	108		(67)		497		(67)
Derivatives designated as hedging instruments | Interest rate risks | Interest Rate Risk
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	1,804		3,628		4,422		9,801
Derivatives not designated as hedging instruments | Currency exchange risks
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	(132)		19		(524)		140
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	(3,125)		502		(1,466)		3,191
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	2,993		(483)		942		(3,051)
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	1,330		315		2,395		790
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	4,876		13,861		11,811		17,857
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	$ (594)	[1]	$ 25	[1]	$ (956)	[1]	$ (1,327)	[1]

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