Stock Repurchases - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	9 Months Ended
	Feb. 09, 2012	Sep. 30, 2012	Sep. 30, 2012
Stock Repurchase Programs [Line Items]
Maximum prevailing market price period, years	2 years
Common stock repurchased, shares outstanding		0	1,372,853
Stock repurchases during period value			$ 50,025,000
Maximum
Stock Repurchase Programs [Line Items]
Amount of authorized repurchase of outstanding common stock	100,000,000