Segment information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Revenue and Operating Profit [Line Items]
Revenues	$ 990.5	$ 935.6	$ 1,962.0	$ 1,871.1
Operating profit	33.2	31.4	50.4	79.0
Capital expenditures			79.7	70.9
Depreciation and amortization			88.6	81.2
Total assets	2,670.5		2,670.5		2,553.9
International [Member]
Segment Revenue and Operating Profit [Line Items]
Revenues	751.8	698.0	1,487.7	1,397.1
Operating profit	48.0	41.3	84.6	107.4
North America [Member]
Segment Revenue and Operating Profit [Line Items]
Revenues	238.7	237.6	474.3	474.0
Operating profit	6.8	11.4	4.4	17.2
Segment operating profit [Member]
Segment Revenue and Operating Profit [Line Items]
Operating profit	54.8	52.7	89.0	124.6
Non Segment [Member]
Segment Revenue and Operating Profit [Line Items]
Operating profit	$ (21.6)	$ (21.3)	$ (38.6)	$ (45.6)