Common and Preferred Stock (Additional Information) (Detail) (USD $)	0 Months Ended	9 Months Ended			1 Months Ended	9 Months Ended
	Nov. 08, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Oct. 27, 2014 Subsequent Event	Sep. 30, 2014 October Settlement
Stockholders Equity Note [Line Items]
Increase in share repurchase authorized amount	$ 300,000,000
Purchase of common stock (in shares)		1,984,337	2,500,000.0
Repurchase of common stock, including subsequent settlements		149,700,000	139,900,000
Purchase of common stock		146,042,000	137,272,000		2,700,000	3,700,000
Remaining authorized repurchase amount		$ 218,200,000
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