Common and Preferred Stock - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended			9 Months Ended		1 Months Ended
	Oct. 22, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Repurchase Of Common Stock	Sep. 30, 2012 Repurchase Of Common Stock	Oct. 30, 2013 Subsequent Event April Settlement
Stockholders Equity Note [Line Items]
Increase in share repurchase authorized amount	$ 200,000,000
Purchase of common stock (in shares)		2,510,306			2,510,406	1,900,000.0
Purchase of common stock		$ 137,272,000	$ 75,174,000		$ 139,900,000	$ 75,200,000	$ 2,700,000
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