Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 31, 2012	Feb. 27, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of Common Stock, shares		12,000,000
Sale of Common Stock, par value		$ 0.01	$ 0.01		$ 0.01		$ 0.01
Sale of Common Stock, Price Per Share		$ 30.83
Proceeds from sale of Common Stock						$ 369,584
Underwriting discounts and estimated transaction expenses payable						376
Weighted average grant date fair value per share					$ 34.06
Repurchase of common stock, maximum value					1,200,000
Repurchase of common stock , shares						619,447
Repurchase of common stock , value						18,597
Remaining value of common stock authorized under repurchase program					415,960
Cash dividend per common share, increase	$ 0.01
Cash dividend per share			$ 0.10	$ 0.09	$ 0.30	$ 0.27
Cash dividends on common stock					$ 37,005	$ 32,182
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash dividend per share	$ 0.09
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash dividend per share	$ 0.10