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				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives					$ (11,087)		$ 16,594
Derivatives designated as hedging instruments | Interest rate risks | Interest rate swaps | Interest expense—borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	638		634		1,915		1,901
Derivatives designated as hedging instruments | Interest rate risks | Interest rate swaps | Gain (Loss) on Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(12)		(7)		(37)		20
Derivatives designated as hedging instruments | Interest rate risks | Interest Rate Risk
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	626		627		1,878		1,921
Derivatives not designated as hedging instruments | Currency exchange risks
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(111)		(322)		(309)		(1,060)
Derivatives not designated as hedging instruments | Currency exchange risks | Loans | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(12,640)		8,101		(12,347)		451
Derivatives not designated as hedging instruments | Currency exchange risks | Foreign exchange forwards | Gain (Loss) on Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	12,529		(8,423)		12,038		(1,511)
Derivatives not designated as hedging instruments | Other derivative instruments | Foreign exchange forwards | Gain (Loss) on Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	886		(411)		1,358		(237)
Derivatives not designated as hedging instruments | Other derivative instruments | Equity warrant assets | Gain (Loss) on Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	13,157		18,780		50,859		29,475
Derivatives not designated as hedging instruments | Other derivative instruments | Other derivatives | Gain (Loss) on Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	$ (22)	[1]	$ (517)	[1]	$ (738)	[1]	$ 55	[1]

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