Derivative Financial Instruments Summary of Derivative Activity and Related Impact on Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	$ 18,287	$ 53,470	$ 22,139
Derivatives designated as hedging instruments | Interest rate risks
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	2,306	2,506	2,503
Derivatives designated as hedging instruments | Interest rate risks | Interest expense-borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	2,341	2,526	2,553
Derivatives designated as hedging instruments | Interest rate risks | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(35)	(20)	(50)
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	37,892	70,963	71,012
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	262	(209)	(796)
Internal Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	(16,676)	(12,735)	(21,636)
Internal Instruments [Member] | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(540)	(358)	(38)
Internal Instruments [Member] | Derivatives not designated as hedging instruments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	(16,676)	(12,735)	(21,636)
Internal Instruments [Member] | Derivatives not designated as hedging instruments | Currency exchange risks | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	16,136	12,377	21,598
Client Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	4,215	115	(4,078)
Client Instruments [Member] | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(1,459)	809	1,003
Client Instruments [Member] | Derivatives not designated as hedging instruments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	4,215	115	(4,078)
Client Instruments [Member] | Derivatives not designated as hedging instruments | Currency exchange risks | Net gains on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	$ (5,674)	$ 694	$ 5,081