Derivatives and Hedging Activities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative [Line Items]
Interest expense	$ 2,592,000	$ 1,421,000	$ 452,000
Interest Rate Swap
Derivative [Line Items]
Interest rate swap, fixed-rate		4.515%
Interest expense		139,000
Interest Rate Swap | Termination
Derivative [Line Items]
Interest expense		$ 267,000