Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Fair Value of Derivatives
Derivative assets	$ 61,598	$ 30,486
Derivative liabilities	64,907	24,939
Notional Amount of Derivatives
Derivative assets	1,306,707	1,255,277
Derivative liabilities	1,579,770	950,105
Cash as collateral for derivative transactions	14,200	21,800
Designated as Hedging Instrument
Fair Value of Derivatives
Derivative assets	0	58
Derivative liabilities	9,872	0
Notional Amount of Derivatives
Derivative assets	0	108,500
Derivative liabilities	108,500	0
Designated as Hedging Instrument | Interest Rate Contracts
Notional Amount of Derivatives
Derivative assets	0	108,500
Derivative liabilities	108,500	0
Designated as Hedging Instrument | Interest Rate Contracts | Other Assets
Fair Value of Derivatives
Derivative assets	0	58
Designated as Hedging Instrument | Interest Rate Contracts | Other Liabilities
Fair Value of Derivatives
Derivative liabilities	9,872	0
Not Designated as Hedging Instruments
Fair Value of Derivatives
Derivative assets	61,598	30,428
Derivative liabilities	55,035	24,939
Notional Amount of Derivatives
Derivative assets	1,306,707	1,146,777
Derivative liabilities	1,471,270	950,105
Not Designated as Hedging Instruments | Interest Rate Contracts
Notional Amount of Derivatives
Derivative assets	825,745	590,334
Derivative liabilities	825,745	590,334
Not Designated as Hedging Instruments | Interest Rate Contracts | Other Assets
Fair Value of Derivatives
Derivative assets	43,569	18,077
Not Designated as Hedging Instruments | Interest Rate Contracts | Other Liabilities
Fair Value of Derivatives
Derivative liabilities	43,569	18,077
Not Designated as Hedging Instruments | Foreign Exchange Contracts
Notional Amount of Derivatives
Derivative assets	1,994	4,392
Derivative liabilities	1,994	4,392
Not Designated as Hedging Instruments | Foreign Exchange Contracts | Other Assets
Fair Value of Derivatives
Derivative assets	10	156
Not Designated as Hedging Instruments | Foreign Exchange Contracts | Other Liabilities
Fair Value of Derivatives
Derivative liabilities	0	134
Not Designated as Hedging Instruments | Forward Sales Contracts
Notional Amount of Derivatives
Derivative assets	15,471	223,841
Derivative liabilities	462,381	173,430
Not Designated as Hedging Instruments | Forward Sales Contracts | Other Assets
Fair Value of Derivatives
Derivative assets	51	1,588
Not Designated as Hedging Instruments | Forward Sales Contracts | Other Liabilities
Fair Value of Derivatives
Derivative liabilities	4,322	474
Not Designated as Hedging Instruments | Written and Purchased Options
Notional Amount of Derivatives
Derivative assets	463,497	328,210
Derivative liabilities	181,150	181,949
Not Designated as Hedging Instruments | Written and Purchased Options | Other Assets
Fair Value of Derivatives
Derivative assets	17,968	10,607
Not Designated as Hedging Instruments | Written and Purchased Options | Other Liabilities
Fair Value of Derivatives
Derivative liabilities	$ 7,144	$ 6,254