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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives			$ (8,214)	$ 4,370
Equity warrant assets
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives			29,666	20,505
Derivatives designated as hedging instruments | Interest rate risks
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 62	$ 577	990	1,745
Derivatives designated as hedging instruments | Interest rate risks | Interest expense—borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	62	580	997	1,778
Derivatives designated as hedging instruments | Interest rate risks | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	0	(3)	(7)	(33)
Derivatives not designated as hedging instruments | Foreign Exchange Contract
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	11	(54)	916	(1,155)
Derivatives not designated as hedging instruments | Foreign Exchange Contract | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(10,550)	1,352	(28,349)	3,067
Derivatives not designated as hedging instruments | Foreign Exchange Contract | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	10,561	(1,406)	29,265	(4,222)
Derivatives not designated as hedging instruments | Other derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(111)	294	539	(1,771)
Derivatives not designated as hedging instruments | Other derivative instruments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(3,871)	(3,194)	(8,350)	(8,780)
Derivatives not designated as hedging instruments | Other derivative instruments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	3,760	3,488	8,889	7,009
Derivatives not designated as hedging instruments | Other derivative instruments | Other derivative contracts | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(38)	31	(524)	(659)
Derivatives not designated as hedging instruments | Equity warrant assets | gains and losses on equity warrant assets [Domain]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 24,922	$ 21,558	$ 42,432	$ 33,252