Common and Preferred Stock (Additional Information) (Detail) (USD $)	0 Months Ended	6 Months Ended			1 Months Ended
	Nov. 08, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Apr. 30, 2014 April Settlement	Apr. 30, 2013 April Settlement
Stockholders Equity Note [Line Items]
Increase in share repurchase authorized amount	$ 300,000,000
Purchase of common stock (in shares)		1,153,384	1,600,000.0
Repurchase of common stock, including subsequent settlements		85,700,000	86,700,000
Purchase of common stock		83,060,000	84,479,000		2,600,000	2,200,000
Remaining authorized repurchase amount		$ 282,200,000
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