Derivative Financial Instruments - Summary of Derivative Activity and Related Impact on Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives			$ 42,295	$ (2,028)
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	$ 631	$ 638	1,903	1,915
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	(8)	(12)	(22)	(37)
Derivatives designated as hedging instruments | Interest rate risks | Interest Rate Risk
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	623	626	1,881	1,878
Derivatives not designated as hedging instruments | Currency exchange risks
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(32)	(111)	(41)	(309)
Derivatives not designated as hedging instruments | Currency exchange risks | Loans | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	186	(12,640)	(11,667)	(12,347)
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	(218)	12,529	11,626	12,038
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	(394)	(22)	(352)	(738)
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	179	886	459	1,358
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	$ 10,685	$ 13,157	$ 54,579	$ 50,859