Derivative Financial Instruments - Total Notional or Contractual Amounts, Fair Value, Collateral and Net Exposure of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Variation Margin	$ 8,600
Derivative Asset	249,243	$ 232,152
Derivative Liability	117,694	108,581
Variation Margin - Notional Amount	433,600
Foreign exchange forwards
Derivative [Line Items]
Fair value, Assets	106,618	95,449
Fair value, Liabilities	(102,439)	(95,454)
Client foreign currency options
Derivative [Line Items]
Fair value, Assets	1,886	1,187
Fair value, Liabilities	(1,886)	(1,187)
Client interest rate derivatives
Derivative [Line Items]
Fair value, Assets	5,070	11,753
Fair value, Liabilities	(13,369)	(11,940)
Derivatives not designated as hedging instruments | Foreign Exchange Contract | Other assets
Derivative [Line Items]
Derivative, Notional Amount	490,255	50,889
Fair value, Assets	6,713	414
Derivatives not designated as hedging instruments | Foreign Exchange Contract | Other liability
Derivative [Line Items]
Derivative, Notional Amount	393,082	425,055
Fair value, Liabilities	10,244	5,201
Derivatives not designated as hedging instruments | Other derivative instruments | Other assets | Other derivative contracts
Derivative [Line Items]
Derivative, Notional Amount	146,954	102,678
Fair value, Assets	1,886	1,187
Derivatives not designated as hedging instruments | Other derivative instruments | Other assets | Client interest rate derivatives
Derivative [Line Items]
Derivative, Notional Amount	287,489	726,984
Fair value, Assets	5,070	11,753
Derivatives not designated as hedging instruments | Other derivative instruments | Other assets | Foreign Exchange Contract
Derivative [Line Items]
Derivative, Notional Amount	2,159,827	2,203,643
Fair value, Assets	99,905	95,035
Derivatives not designated as hedging instruments | Other derivative instruments | Other liability | Other derivative contracts
Derivative [Line Items]
Derivative, Notional Amount	146,954	102,678
Fair value, Liabilities	1,886	1,187
Derivatives not designated as hedging instruments | Other derivative instruments | Other liability | Client interest rate derivatives
Derivative [Line Items]
Derivative, Notional Amount	770,653	782,586
Fair value, Liabilities	13,369	11,940
Derivatives not designated as hedging instruments | Other derivative instruments | Other liability | Foreign Exchange Contract
Derivative [Line Items]
Derivative, Notional Amount	2,077,802	2,092,207
Fair value, Liabilities	$ 92,195	$ 90,253