Derivative Financial Instruments Total Notional or Contractual Amounts, Fair Value, Collateral and Net Exposure of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Fair value	$ 108,389	$ 78,947
Fair value	(108,581)	(64,438)
Net Exposure Derivative Instruments	119,841	132,964
Fair value	123,571	145,632
Collateral	3,730	12,668
Derivatives designated as hedging instruments | Interest rate risks | Other Assets
Derivative [Line Items]
Notional or Contractual Amount	0	45,964
Fair value	0	810
Collateral	0	89
Net Exposure	0	721
Derivatives not designated as hedging instruments | Foreign Exchange Contract [Member]
Derivative [Line Items]
Fair value	(4,787)	2,089
Net Exposure Derivative Instruments	(4,826)	2,089
Collateral	39	0
Derivatives not designated as hedging instruments | Foreign Exchange Contract [Member] | Other Assets
Derivative [Line Items]
Notional or Contractual Amount	50,889	219,950
Fair value	414	3,057
Collateral	39	0
Net Exposure	375	3,057
Derivatives not designated as hedging instruments | Foreign Exchange Contract [Member] | Other liability
Derivative [Line Items]
Notional or Contractual Amount	425,055	54,338
Fair value	(5,201)	(968)
Net Exposure Derivative Instruments Liabilities	(5,201)	(968)
Collateral	0	0
Derivatives not designated as hedging instruments | Other derivative instruments | Equity warrant assets | Other Assets
Derivative [Line Items]
Notional or Contractual Amount	211,253	211,434
Fair value	123,763	131,123
Collateral	0	0
Net Exposure	123,763	131,123
Derivatives not designated as hedging instruments | Other derivative instruments | Foreign Exchange Contract [Member] | Other Assets
Derivative [Line Items]
Notional or Contractual Amount	2,203,643	1,251,308
Fair value	95,035	54,587
Collateral	3,691	12,579
Net Exposure	91,344	42,008
Derivatives not designated as hedging instruments | Other derivative instruments | Foreign Exchange Contract [Member] | Other liability
Derivative [Line Items]
Notional or Contractual Amount	2,092,207	1,068,991
Fair value	(90,253)	(43,317)
Net Exposure Derivative Instruments Liabilities	(90,253)	(43,317)
Collateral	0	0
Derivatives not designated as hedging instruments | Other derivative instruments | Other derivatives
Derivative [Line Items]
Fair value	4,595	11,610
Net Exposure Derivative Instruments	904	(969)
Collateral	3,691	12,579
Derivatives not designated as hedging instruments | Other derivative instruments | Other derivatives | Other Assets
Derivative [Line Items]
Notional or Contractual Amount	102,678	775,000
Fair value	1,187	10,383
Collateral	0	0
Net Exposure	1,187	10,383
Derivatives not designated as hedging instruments | Other derivative instruments | Other derivatives | Other liability
Derivative [Line Items]
Notional or Contractual Amount	102,678	775,000
Fair value	(1,187)	(10,383)
Net Exposure Derivative Instruments Liabilities	(1,187)	(10,383)
Collateral	0	0
Derivatives not designated as hedging instruments | Other derivative instruments | Client interest rate derivatives | Other Assets
Derivative [Line Items]
Notional or Contractual Amount	726,984	583,511
Fair value	11,753	10,110
Collateral	0	0
Net Exposure	11,753	10,110
Derivatives not designated as hedging instruments | Other derivative instruments | Client interest rate derivatives | Other liability
Derivative [Line Items]
Notional or Contractual Amount	782,586	627,639
Fair value	(11,940)	(9,770)
Net Exposure Derivative Instruments Liabilities	(11,940)	(9,770)
Collateral	$ 0	$ 0