Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value of Derivatives
Derivative Asset	$ 31,779	$ 38,886
Derivative Liability	28,453	30,209
Notional Amount of Derivatives
Derivative assets	1,636,857	1,565,509
Derivative liabilities	1,617,136	1,528,184
Designated as Hedging Instruments
Fair Value of Derivatives
Derivative Asset	0	0
Derivative Liability	1,027	525
Notional Amount of Derivatives
Derivative assets	0	0
Derivative liabilities	108,500	108,500
Designated as Hedging Instruments | Interest rate contracts
Notional Amount of Derivatives
Derivative assets	0	0
Derivative liabilities	108,500	108,500
Designated as Hedging Instruments | Interest rate contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	0	0
Designated as Hedging Instruments | Interest rate contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	1,027	525
Not Designated as Hedging Instruments
Notional Amount of Derivatives
Derivative assets	1,636,857	1,565,509
Derivative liabilities	1,508,636	1,419,684
Not Designated as Hedging Instruments | Other Assets
Fair Value of Derivatives
Derivative Asset	31,779	38,886
Not Designated as Hedging Instruments | Other Liabilities
Fair Value of Derivatives
Derivative Liability	27,426	29,684
Not Designated as Hedging Instruments | Interest rate contracts
Notional Amount of Derivatives
Derivative assets	1,129,079	1,033,955
Derivative liabilities	1,129,079	1,033,955
Not Designated as Hedging Instruments | Interest rate contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	19,752	20,719
Not Designated as Hedging Instruments | Interest rate contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	17,885	20,719
Not Designated as Hedging Instruments | Foreign exchange contracts
Notional Amount of Derivatives
Derivative assets	831	4,474
Derivative liabilities	831	4,474
Not Designated as Hedging Instruments | Foreign exchange contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	17	27
Not Designated as Hedging Instruments | Foreign exchange contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	17	26
Not Designated as Hedging Instruments | Forward sales contracts
Notional Amount of Derivatives
Derivative assets	174,506	229,181
Derivative liabilities	123,785	120,567
Not Designated as Hedging Instruments | Forward sales contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	493	6,014
Not Designated as Hedging Instruments | Forward sales contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	597	794
Not Designated as Hedging Instruments | Written and purchased options
Notional Amount of Derivatives
Derivative assets	323,890	289,115
Derivative liabilities	165,946	154,170
Not Designated as Hedging Instruments | Written and purchased options | Other Assets
Fair Value of Derivatives
Derivative Asset	11,517	12,125
Not Designated as Hedging Instruments | Written and purchased options | Other Liabilities
Fair Value of Derivatives
Derivative Liability	8,894	8,098
Not Designated as Hedging Instruments | Other contracts
Notional Amount of Derivatives
Derivative assets	8,551	8,784
Derivative liabilities	88,995	106,518
Not Designated as Hedging Instruments | Other contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	0	1
Not Designated as Hedging Instruments | Other contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	$ 33	$ 47