Derivative Financial Instruments - 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, 2013		Jun. 30, 2012		Jun. 30, 2013	Jun. 30, 2012
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	$ 633		$ 1,696		$ 1,267	$ 3,925
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	(33)		108		27	497
Derivatives designated as hedging instruments | Interest rate risks | Interest Rate Risk
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	600		1,804		1,294	4,422
Derivatives not designated as hedging instruments | Currency exchange risks
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivative instruments	126		(374)		(738)	(540)
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	(586)		(3,367)		(7,650)	(1,482)
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	712		2,993		6,912	942
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	1,013		1,330		1,810	2,395
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	7,190		4,876		10,695	11,811
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	$ 94	[1]	$ (594)	[1]	$ 572	$ (956)

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