Other Intangible Assets - Summary of Other Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Gross cost at January 1	$ 295.8	$ 248.6
Acquisitions	0.0	33.5
Internally developed software	0.8	0.0
Exchange effect	1.2	0.1
Gross cost at March 31	297.8	282.2
Accumulated amortization at January 1	(132.5)	(104.2)
Amortization expense	(6.7)	(6.9)
Exchange effect	(0.3)	0.1
Accumulated amortization at March 31	(139.5)	(111.0)
Net book amount at March 31	$ 158.3	$ 171.2	$ 163.3