Commitments and Contingencies - Consolidated Statements of Financial Condition Related to Fair Value of Derivative Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 1,140,406	$ 1,191,591
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge Interest Rate Caps and Swaps [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,007,000	1,007,000
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedge Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative, Notional Amount	133,406	184,591
Derivatives Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	419,706	306,616
Derivatives Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative, Notional Amount	378,849	259,832
Derivatives Not Designated as Hedging Instrument [Member] | Mortgage Banking Derivatives [Member]
Derivative [Line Items]
Derivative, Notional Amount	40,857	46,784
Other Assets [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	8,486	9,982
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	2,229	9,883
Other Assets [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedge Interest Rate Swaps [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	6,257	99
Other Assets [Member] | Derivatives Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	12,501	5,140
Other Assets [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	12,464	4,823
Other Assets [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Mortgage Banking Derivatives [Member]
Derivative [Line Items]
Asset Derivatives, Fair Value	37	317
Other Liabilities [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	20,784	15,616
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	19,302	10,925
Other Liabilities [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedge Interest Rate Swaps [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	1,482	4,691
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	12,546	4,970
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	12,455	4,823
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Mortgage Banking Derivatives [Member]
Derivative [Line Items]
Liability Derivatives, Fair Value	$ 91	$ 147