Derivatives - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Interest rate swap [Member]	Dec. 31, 2012 Interest rate swap [Member]
Derivative [Line Items]
Notional amount of interest rate derivatives		$ 140,000,000	$ 140,000,000
Variable rate term loan agreement maturity	June 2013
Derivative, net hedge ineffectiveness gain (loss)	0
Amount reclassified to decrease to interest expense	100,000
Termination value of derivatives in a net liability position	18,600,000
Collateral obligations for derivative counterparties	$ 15,000,000