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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest rate risks | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	$ 0	$ 375	$ 0	$ 928
Interest rate risks | Derivatives designated as hedging instruments | Interest expense—borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	0	381	0	935
Interest rate risks | Derivatives designated as hedging instruments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	0	(6)	0	(7)
Currency exchange risk | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	140	42	(446)	905
Currency exchange risk | Derivatives not designated as hedging instruments | Revaluations of internal foreign currency instruments, net | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	(319)	14,596	2,607	18,704
Currency exchange risk | Derivatives not designated as hedging instruments | Foreign exchange forward contracts, net | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	459	(14,554)	(3,053)	(17,799)
Other derivative instruments | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	96	185	635	650
Other derivative instruments | Derivatives not designated as hedging instruments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	(10)	(210)	421	(486)
Other derivative instruments | Derivatives not designated as hedging instruments | Revaluations of internal foreign currency instruments, net | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	(2,748)	2,375	4,905	5,129
Other derivative instruments | Derivatives not designated as hedging instruments | Foreign exchange forward contracts, net | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	2,844	(2,190)	(4,270)	(4,479)
Equity warrant assets
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives			24,940	9,053
Equity warrant assets | Derivatives not designated as hedging instruments | Gains on equity warrant assets, net
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives	$ 19,061	$ 10,820	$ 38,252	$ 17,510