Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Cash Dividend on Common Stock	$ 0.85	$ 0.80
Aggregated Dividend Paid	$ 43.6
Dividend payable date declared	Feb. 23, 2018
Common stock Dividend Payable Date	Apr. 16, 2018
Dividend payable date of record	Mar. 30, 2018