Derivative Instruments and Hedging Activities - Consolidated Statements of Financial Condition Related to Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Interest Rate Caps and Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	$ 0	$ 0
Liability Derivatives, Fair Value	41,759	33,239
Derivatives Designated as Hedging Instruments
Derivative [Line Items]
Asset Derivatives, Fair Value	7,125	8,486
Liability Derivatives, Fair Value	25,006	20,784
Notional Amount, Fair Value	1,140,309	1,140,406
Derivatives Designated as Hedging Instruments | Cash Flow Hedge | Interest Rate Caps and Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	1,958	2,229
Liability Derivatives, Fair Value	23,628	19,302
Notional Amount, Fair Value	1,007,000	1,007,000
Derivatives Designated as Hedging Instruments | Designated as Fair Value Hedge | Interest Rate Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	5,167	6,257
Liability Derivatives, Fair Value	1,378	1,482
Notional Amount, Fair Value	133,309	133,406
Derivatives Not Designated as Hedging Instrument
Derivative [Line Items]
Asset Derivatives, Fair Value	16,857	12,501
Liability Derivatives, Fair Value	16,795	12,546
Notional Amount, Fair Value	516,972	419,706
Derivatives Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative [Line Items]
Asset Derivatives, Fair Value	16,756	12,464
Liability Derivatives, Fair Value	16,753	12,455
Notional Amount, Fair Value	500,473	378,849
Derivatives Not Designated as Hedging Instrument | Mortgage Banking Derivatives
Derivative [Line Items]
Asset Derivatives, Fair Value	101	37
Liability Derivatives, Fair Value	42	91
Notional Amount, Fair Value	$ 16,499	$ 40,857