Common and Preferred Stock (Additional Information) (Detail) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended
	Nov. 06, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Stockholders Equity Note [Line Items]
Increase in share repurchase authorized amount	$ 400,000
Purchase of common stock (in shares)		2,401,729	2,000,000
Repurchase of common stock, including subsequent settlements		$ 179,400	$ 149,700
Purchase of common stock		177,772	146,042
Remaining authorized repurchase amount		$ 366,000
Common stock, authorized (in shares)		150,000,000		150,000,000
Common stock, par value (in dollars per share)		$ 0.01		$ 0.01
Preferred stock, authorized (in shares)		5,000,000		5,000,000
Preferred stock, par value (in dollars per share)		$ 0.01		$ 0.01
Preferred stock, issued (in shares)		0		0
October Settlement
Stockholders Equity Note [Line Items]
Purchase of common stock		$ 4,300	$ 3,700