Goodwill and Identifiable Intangible Assets, Net - Additional information (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill And Other Intangible Assets
Goodwill impairment		$ 33.6	$ 61.8	$ 33.6	$ 61.8	$ 0.0
Impairment on intangible assets	$ 10.1			10.1	0.1	$ 0.0
RANA
Goodwill And Other Intangible Assets
Goodwill impairment				33.6	$ 61.8
Impairment on intangible assets				$ 10.1