Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Equity [Line Items]
Cash Dividend on Common Stock	$ 0.75	$ 0.75	$ 0.75	$ 0.70	$ 2.25	$ 2.00
Aggregated Dividend Paid	$ 38,300,000	$ 38,300,000	$ 38,200,000
Dividend payable date declared	Sep. 14, 2016	Jun. 13, 2016	Feb. 26, 2016
Common stock Dividend Payable Date	Oct. 14, 2016	Jul. 15, 2016	Apr. 15, 2016
Dividend payable date of record	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
2015 Stock Repurchase Program [Member]
Schedule Of Equity [Line Items]
Authorized amount for share repurchase program	$ 100,000,000				$ 100,000,000
Company repurchased, shares			0.5
Repurchase of Company stock for retirement			$ 24,800,000