Schedule of Activity Related to Redeemable Preferred Stock (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Balance, December 31, 2014	$ 21.9	$ 0.0
Fair value of Redeemable Preferred Stock issued		19.6
Dividends on Redeemable Preferred Stock, in-kind	2.0	1.5	$ 0.0
Accretion of fair value adjustment to Redeemable Preferred Stock	1.0	0.8	0.0
Balance, December 31, 2015	$ 24.9	$ 21.9	$ 0.0