Derivative Instruments and Hedging Activities - Consolidated Statements of Financial Condition Related to Fair Value of Derivative Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Notional Amount, Fair Value	$ 1,140,358	$ 1,140,406
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge Interest Rate Caps and Swaps [Member]
Derivative [Line Items]
Notional Amount, Fair Value	1,007,000	1,007,000
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedge Interest Rate Swaps [Member]
Derivative [Line Items]
Notional Amount, Fair Value	133,358	133,406
Derivatives Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount, Fair Value	414,352	419,706
Derivatives Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Notional Amount, Fair Value	393,283	378,849
Derivatives Not Designated as Hedging Instrument [Member] | Mortgage Banking Derivatives [Member]
Derivative [Line Items]
Notional Amount, Fair Value	21,069	40,857
Other Assets [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	10,896	8,486
Other Assets [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge Interest Rate Caps and Swaps [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	1,897	2,229
Other Assets [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedge Interest Rate Swaps [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	8,999	6,257
Other Assets [Member] | Derivatives Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	18,874	12,501
Other Assets [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	18,832	12,464
Other Assets [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Mortgage Banking Derivatives [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	42	37
Other Liabilities [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	28,240	20,784
Other Liabilities [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge Interest Rate Caps and Swaps [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	26,704	19,302
Other Liabilities [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedge Interest Rate Swaps [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	1,536	1,482
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	18,880	12,546
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	18,828	12,455
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Mortgage Banking Derivatives [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	$ 52	$ 91