Stock Repurchase Program - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended	6 Months Ended
	Nov. 30, 2011	Apr. 30, 2008	Jun. 30, 2013	Jun. 30, 2013
Equity [Abstract]
Repurchase of authorized common stock	$ 80,000,000	$ 50,000,000
Repurchase of shares			1,643,875	1,643,875
Repurchase of shares during period			268,000
Repurchase of shares, Value			41,891,000	41,891,000
Repurchase of shares during period, Value			11,891,000	11,891,000
Repurchase of remaining shares, Value				$ 8,109,000