Derivative Financial Instruments - Summary of Derivative Activity and Related Impact on Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives			$ 33,030	$ (14,566)
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	$ 634	$ 638	1,272	1,277
Derivatives designated as hedging instruments | Interest rate risks | Interest rate swaps | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(11)	(13)	(14)	(25)
Derivatives designated as hedging instruments | Interest rate risks | Interest Rate Risk
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	623	625	1,258	1,252
Derivatives not designated as hedging instruments | Currency exchange risks
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	132	(147)	(9)	(198)
Derivatives not designated as hedging instruments | Currency exchange risks | Loans | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	8,306	(685)	(11,853)	293
Derivatives not designated as hedging instruments | Currency exchange risks | Foreign exchange forwards | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(8,174)	538	11,844	(491)
Derivatives not designated as hedging instruments | Other derivative instruments | Other derivatives | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	99	(249)	42	(716)
Derivatives not designated as hedging instruments | Other derivative instruments | Foreign exchange forwards | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	787	170	280	472
Derivatives not designated as hedging instruments | Other derivative instruments | Equity warrant assets | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	$ 23,616	$ 12,329	$ 43,894	$ 37,702