Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended						9 Months Ended
	Oct. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Jul. 31, 2015	Feb. 28, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend paid per share		$ 0.17	$ 0.17	$ 0.17	$ 0.16	$ 0.16	$ 0.16
Aggregate dividend declared for the year								$ 9,200,000	$ 9,100,000
Cash dividends declared per common share		$ 0.17			$ 0.16			$ 0.51	$ 0.48
Increase in authorized to purchase of common stock under the stock repurchase program										$ 25,000,000	$ 25,000,000
Authorized to purchase of common stock under the stock repurchase program		$ 460,000,000						$ 460,000,000
Repurchase of common Stock		0.2			0.3			0.5	1.8
Cumulative aggregate cost of repurchase of common stock		$ 6,900,000			$ 11,600,000			$ 18,600,000	$ 66,600,000
Cumulative repurchase of common stock		14.9						14.9
Aggregate cost of repurchase of common stock								$ 420,900,000
Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash dividends declared per common share	$ 0.17
Dividend payable date	Dec. 16, 2015
Dividend payable record date	Dec. 02, 2015