Derivatives and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	$ 1,700,000		$ 1,700,000
Derivative Collateral	100.00%		100.00%
Derivative Collateral Posted	0		0
Other Credit Enhancements
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	1,000,000		1,000,000
Credit Default Option [Member]
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	12,500,000		12,500,000
Termination
Derivative [Line Items]
Fair Value of Credit Risk Derivatives	13,100,000		13,100,000
Net Liability Position [Member]
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	14,300,000		14,300,000
Designated as Hedging Instrument [Member] | Interest Rate Caps
Derivative [Line Items]
Derivative, Number of Instruments Held	6		6
Derivative, Notional Amount	165,000,000		165,000,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held	9		9
Derivative, Notional Amount	625,000,000		625,000,000
Designated as Hedging Instrument [Member] | Interest Expense
Derivative [Line Items]
Loss on Cash Flow Hedge Ineffectiveness	(25,000)	1,000	(88,000)
Gain on Cash Flow Hedge Ineffectiveness				26,000
Change in fair value of interest rate derivatives included in AOCI and expected to be reclassified in the next 12 months			7,500,000
Not Designated as Hedging Instrument [Member] | Interest Rate Caps
Derivative [Line Items]
Derivative, Number of Instruments Held	14		14
Derivative, Notional Amount	90,326,031		90,326,031
Not Designated as Hedging Instrument [Member] | Interest Expense
Derivative [Line Items]
Derivative, Loss on Derivative	$ (10,000)	$ 5,000	$ (138,000)	$ (8,000)