Other Noninterest Income and Other Noninterest Expense - Summary of Other Noninterest Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Noninterest Income [Line Items]
Fund management fees	$ 5,736	$ 5,169
Other (3)	6,570	5,924
Total other noninterest income	12,259	12,421
Client Instruments
Other Noninterest Income [Line Items]
Gains (losses) on revaluation of internal foreign currency instruments, net (2)	(47)	1,328
Derivatives not designated as hedging instruments | Foreign Exchange Contract
Other Noninterest Income [Line Items]
Unrealized Gain (Loss) on Derivatives	(586)	863
Derivatives not designated as hedging instruments | Other derivative instruments
Other Noninterest Income [Line Items]
Unrealized Gain (Loss) on Derivatives	539	465
Other noninterest income | Derivatives not designated as hedging instruments | Foreign Exchange Contract
Other Noninterest Income [Line Items]
Unrealized Gain (Loss) on Derivatives	(3,512)	(3,245)
Other noninterest income | Derivatives not designated as hedging instruments | Other derivative instruments
Other Noninterest Income [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (7,114)	$ (2,289)