Income Taxes - Schedule of Changes in Amount of Uncertain Tax Positions (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unrecognized liabilities:
Balance at the beginning of the period	$ 16.8	$ 12.2	$ 16.8	$ 16.8
Lapse of applicable statute of limitations	$ (3.0)	0.0	(4.6)	0.0
Balance at the end of the period		$ 12.2	$ 12.2	$ 16.8