Segment information (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Revenue and Operating Profit [Line Items]
Revenues	$ 995.8	$ 776.1	$ 2,888.4	$ 2,240.9
Operating profit	62.5	44.1	119.9	99.4
International [Member]
Segment Revenue and Operating Profit [Line Items]
Revenues	751.3	547.4	2,158.1	1,556.1
Operating profit	61.4	52.6	132.8	110.9
North America [Member]
Segment Revenue and Operating Profit [Line Items]
Revenues	$ 244.5	$ 228.7	$ 730.3	$ 684.8
Operating profit	8.7	5.4	25.9	26.1
Segment operating profit [Member]
Segment Revenue and Operating Profit [Line Items]
Operating profit	70.1	58.0	158.7	137.0
Non Segment [Member]
Segment Revenue and Operating Profit [Line Items]
Operating profit	(7.6)	(13.9)	(38.8)	(37.6)