Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Loss related to ineffective portion of derivatives recognized in other expense, net	$ 286,000	$ 0
Reclassified as an increase to interest expense, expected during the next 12 months	2,916,000
Tax benefit on unrealized loss on derivatives	546,000
Termination value of derivatives in a net liability position	2,372,000
Collateral posted relating to credit risk-related contingent features	0
Combined Interest Rate Cash Flow Hedges, All Swaps [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of interest rate swap	1,000,000,000
Number of outstanding interest rate derivatives	3
Not Designated as Hedge Accounting Relationships [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives outstanding	$ 0		$ 0