Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Summary of Intangible assets
Gross cost at January 1			$ 51.2	$ 48.1
Capitalization of internally developed software and other costs			6.4	0
Exchange effect			0.2	0.2
Gross cost at September 30	57.8	48.3	57.8	48.3
Accumulated amortization at January 1			(33.5)	(29.1)
Amortization expense	(1.1)	(1.1)	(3.1)	(3.4)
Exchange effect			(0.2)	(0.2)
Accumulated amortization at September 30	(36.8)	(32.7)	(36.8)	(32.7)
Net book amount at September 30	$ 21.0	$ 15.6	$ 21.0	$ 15.6	$ 17.7