Common and Preferred Stock (Additional Information) (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	6 Months Ended
	Nov. 06, 2014	Jul. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Stockholders Equity Note [Line Items]
Increase in share repurchase authorized amount	$ 400,000
Purchase of common stock (in shares)			1,490,582	1,200,000
Repurchase of common stock, including subsequent settlements			$ 113,300	$ 85,700
Purchase of common stock		$ 2,600	113,592	$ 83,060
Remaining authorized repurchase amount			$ 432,200
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			$ 2,300