Derivative Financial Instruments - Total Notional or Contractual Amounts, Fair Value, Collateral and Net Exposure of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Fair Value, Derivative Assets	$ 88,165	$ 108,389
Fair Value, Derivative Liabilities	91,321	108,581
Variation Margin	8,700
Variation Margin - Notional Amount	302,400
Foreign exchange forwards
Derivative [Line Items]
Fair Value, Derivative Assets	80,427	95,449
Fair Value, Derivative Liabilities	74,687	95,454
Client foreign currency options
Derivative [Line Items]
Fair Value, Derivative Assets	1,476	1,187
Fair Value, Derivative Liabilities	1,478	1,187
Client interest rate derivatives
Derivative [Line Items]
Fair Value, Derivative Assets	6,262	11,753
Fair Value, Derivative Liabilities	15,156	11,940
Derivatives not designated as hedging instruments
Derivative [Line Items]
Fair Value, Derivative Assets	235,132	232,152
Fair Value, Derivative Liabilities	91,321	108,581
Derivatives not designated as hedging instruments | Foreign exchange forwards | Other assets
Derivative [Line Items]
Derivative Assets, Notional or Contractual Amount	241,360	50,889
Fair Value, Derivative Assets	2,842	414
Derivatives not designated as hedging instruments | Foreign exchange forwards | Other liability
Derivative [Line Items]
Derivative Liabilities, Notional or Contractual Amount	397,153	425,055
Fair Value, Derivative Liabilities	4,370	5,201
Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Derivative [Line Items]
Derivative Assets, Notional or Contractual Amount	223,868	211,253
Fair Value, Derivative Assets	146,967	123,763
Derivatives not designated as hedging instruments | Client foreign exchange forwards | Other assets
Derivative [Line Items]
Derivative Assets, Notional or Contractual Amount	2,523,524	2,203,643
Fair Value, Derivative Assets	77,585	95,035
Derivatives not designated as hedging instruments | Client foreign exchange forwards | Other liability
Derivative [Line Items]
Derivative Liabilities, Notional or Contractual Amount	2,390,294	2,092,207
Fair Value, Derivative Liabilities	70,317	90,253
Derivatives not designated as hedging instruments | Client foreign currency options | Other assets
Derivative [Line Items]
Derivative Assets, Notional or Contractual Amount	91,125	102,678
Fair Value, Derivative Assets	1,476	1,187
Derivatives not designated as hedging instruments | Client foreign currency options | Other liability
Derivative [Line Items]
Derivative Liabilities, Notional or Contractual Amount	91,149	102,678
Fair Value, Derivative Liabilities	1,478	1,187
Derivatives not designated as hedging instruments | Client interest rate derivatives | Other assets
Derivative [Line Items]
Derivative Assets, Notional or Contractual Amount	937,808	726,984
Fair Value, Derivative Assets	6,262	11,753
Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liability
Derivative [Line Items]
Derivative Liabilities, Notional or Contractual Amount	1,335,830	782,586
Fair Value, Derivative Liabilities	$ 15,156	$ 11,940