Derivative Financial Instruments - Total Notional or Contractual Amounts, Fair Value, Collateral and Net Exposure of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Fair Value, Derivative Assets	$ 105,780	$ 108,389
Fair Value, Derivative Liabilities	(97,204)	(108,581)
Fair Value, Derivative Assets	105,780	108,389
Net Amounts of Liabilities Presented in the Statement of Financial Position	97,204	108,581
Variation Margin	5,800
Variation Margin - Notional Amount	281,800
Foreign exchange forwards
Derivative [Line Items]
Fair Value, Derivative Assets	97,645	95,449
Fair Value, Derivative Liabilities	(82,959)	(95,454)
Fair Value, Derivative Assets	97,645	95,449
Net Amounts of Liabilities Presented in the Statement of Financial Position	82,959	95,454
Client foreign currency options
Derivative [Line Items]
Fair Value, Derivative Assets	1,713	1,187
Fair Value, Derivative Liabilities	(1,713)	(1,187)
Fair Value, Derivative Assets	1,713	1,187
Net Amounts of Liabilities Presented in the Statement of Financial Position	1,713	1,187
Client interest rate derivatives
Derivative [Line Items]
Fair Value, Derivative Assets	6,422	11,753
Fair Value, Derivative Liabilities	(12,532)	(11,940)
Fair Value, Derivative Assets	6,422	11,753
Net Amounts of Liabilities Presented in the Statement of Financial Position	12,532	11,940
Derivatives not designated as hedging instruments
Derivative [Line Items]
Fair Value, Derivative Assets	249,505	232,152
Net Amounts of Liabilities Presented in the Statement of Financial Position	97,204	108,581
Derivatives not designated as hedging instruments | Foreign exchange forwards | Other assets
Derivative [Line Items]
Notional or Contractual Amount	501,372	50,889
Fair Value, Derivative Assets	16,250	414
Derivatives not designated as hedging instruments | Foreign exchange forwards | Other liability
Derivative [Line Items]
Notional or Contractual Amount	243,969	425,055
Fair Value, Derivative Liabilities	9,636	5,201
Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Derivative [Line Items]
Notional or Contractual Amount	227,490	211,253
Fair Value, Derivative Assets	143,725	123,763
Derivatives not designated as hedging instruments | Client foreign exchange forwards | Other assets
Derivative [Line Items]
Notional or Contractual Amount	2,582,993	2,203,643
Fair Value, Derivative Assets	81,395	95,035
Derivatives not designated as hedging instruments | Client foreign exchange forwards | Other liability
Derivative [Line Items]
Notional or Contractual Amount	2,305,484	2,092,207
Fair Value, Derivative Liabilities	73,323	90,253
Derivatives not designated as hedging instruments | Client foreign currency options | Other assets
Derivative [Line Items]
Notional or Contractual Amount	107,907	102,678
Fair Value, Derivative Assets	1,713	1,187
Derivatives not designated as hedging instruments | Client foreign currency options | Other liability
Derivative [Line Items]
Notional or Contractual Amount	107,907	102,678
Fair Value, Derivative Liabilities	1,713	1,187
Derivatives not designated as hedging instruments | Client interest rate derivatives | Other assets
Derivative [Line Items]
Notional or Contractual Amount	919,033	726,984
Fair Value, Derivative Assets	6,422	11,753
Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liability
Derivative [Line Items]
Notional or Contractual Amount	1,274,209	782,586
Fair Value, Derivative Liabilities	$ 12,532	$ 11,940