Other Intangible Assets - Summary of Other Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Gross cost at January 1			$ 247.6	$ 175.5
Capitalization of internally developed software			7.0	6.1
Exchange effect			0.1	0.0
Disposal of subsidiary	$ (7.7)	$ 0.0	(7.7)	0.0
Gross cost at September 30	247.0	181.6	247.0	181.6
Accumulated amortization at January 1			(66.5)	(48.7)
Amortization expense	(5.2)	(3.9)	(15.6)	(12.7)
Exchange effect			0.0	0.0
Disposal of subsidiary			7.7	0.0
Accumulated amortization at September 30	(74.4)	(61.4)	(74.4)	(61.4)
Net book amount at September 30	$ 172.6	$ 120.2	$ 172.6	$ 120.2	$ 181.1