Derivative Instruments and Hedging Activities - Consolidated Statements of Financial Condition Related to Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Interest Rate Caps and Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	$ 0	$ 0
Liability Derivatives, Fair Value	57,026	33,239
Derivatives Designated as Hedging Instruments
Derivative [Line Items]
Asset Derivatives, Fair Value	10,722	8,486
Liability Derivatives, Fair Value	33,752	20,784
Notional Amount, Fair Value	1,040,260	1,140,406
Derivatives Designated as Hedging Instruments | Cash Flow Hedge | Interest Rate Caps and Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	1,253	2,229
Liability Derivatives, Fair Value	32,281	19,302
Notional Amount, Fair Value	907,000	1,007,000
Derivatives Designated as Hedging Instruments | Designated as Fair Value Hedge | Interest Rate Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	9,469	6,257
Liability Derivatives, Fair Value	1,471	1,482
Notional Amount, Fair Value	133,260	133,406
Derivatives Not Designated as Hedging Instrument
Derivative [Line Items]
Asset Derivatives, Fair Value	23,392	12,501
Liability Derivatives, Fair Value	23,592	12,546
Notional Amount, Fair Value	590,425	419,706
Derivatives Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	23,278	12,464
Liability Derivatives, Fair Value	23,274	12,455
Notional Amount, Fair Value	528,767	378,849
Derivatives Not Designated as Hedging Instrument | Mortgage Banking Derivatives
Derivative [Line Items]
Asset Derivatives, Fair Value	114	37
Liability Derivatives, Fair Value	318	91
Notional Amount, Fair Value	$ 61,658	$ 40,857