Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule Of Equity [Line Items]
Cash Dividend on Common Stock	$ 0.75	$ 0.75	$ 0.65	$ 1.50	$ 1.30
Aggregated Dividend Paid	$ 38,300,000	$ 38,200,000
Dividend payable date declared	Jun. 13, 2016	Feb. 26, 2016
Common stock Dividend Payable Date	Jul. 15, 2016	Apr. 15, 2016
Dividend payable date of record	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