Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	May 14, 2013 Swap	Sep. 30, 2014 Interest Rate Swaps [Member] Swap	May 14, 2013 Interest Rate Swaps [Member] Swap	Aug. 23, 2012 Interest Rate Swaps [Member] Swap	Sep. 30, 2014 Not Designated as Hedge Accounting Relationships [Member]	Dec. 31, 2013 Not Designated as Hedge Accounting Relationships [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives outstanding							$ 0	$ 0
Notional amount of interest rate swap				1,000,000,000	550,000,000	550,000,000
Number of outstanding interest rate derivatives				3	2	2
Number of restructured interest rate swaps			2
Reclassified as an increase to interest expense, expected during the next 12 months	2,901,000	2,901,000
Tax expense on unrealized gain on derivatives	664,000	4,000
Termination value of derivatives in net liability position	121,000	121,000
Collateral posted relating to credit risk-related contingent features	$ 0	$ 0