Goodwill and Identifiable Intangible Assets, Net - Goodwill rollforward (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Goodwill, Beginning Balance			$ 42.2	$ 104.3
Impairment	$ (33.6)	$ (61.8)	(33.6)	(61.8)	$ 0.0
Currency translation adjustments			1.2	(0.3)
Goodwill, Ending Balance		42.2	9.8	42.2	104.3
RANA
Goodwill
Goodwill, Beginning Balance			33.6	95.4
Impairment			(33.6)	(61.8)
Goodwill, Ending Balance		33.6		33.6	95.4
RAEU
Goodwill
Goodwill, Beginning Balance			8.6	8.9
Currency translation adjustments			1.2	(0.3)
Goodwill, Ending Balance		$ 8.6	$ 9.8	$ 8.6	$ 8.9