Derivatives and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	$ 3,100,000		$ 3,100,000
Derivative Collateral	100.00%		100.00%
Derivative Collateral Posted	0		0
Other Credit Enhancements
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	2,100,000		2,100,000
Credit Default Option [Member]
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	16,600,000		16,600,000
Termination
Derivative [Line Items]
Fair Value of Credit Risk Derivatives	18,000,000		18,000,000
Net Liability Position [Member]
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	19,600,000		19,600,000
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	11		11
Derivative, Notional Amount	675,000,000		675,000,000
Designated as Hedging Instrument [Member] | Interest Expense
Derivative [Line Items]
Loss on Cash Flow Hedge Ineffectiveness	(59,000)		(63,000)
Gain on Cash Flow Hedge Ineffectiveness		22,000		26,000
Change in fair value of interest rate derivatives included in AOCI and expected to be reclassified in the next 12 months			8,800,000
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	(59,000)		(128,000)	(3,000)
Derivative, Gain on Derivative		$ 10,000