Dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Dividends [Abstract]
Dividends declared and paid	$ 9.7	$ 9.9	$ 29.2	$ 29.7
Quarterly cash dividend	$ 0.10	$ 0.10