Pension plans 5 (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, long-term investment period one (in years)	10
Defined benefit plan, long-term investment period two (in years)	15
Defined benefit plan, long-term investment period three (in years)	20
Defined benefit plan, long-term investment period four (in years)	25
Defined benefit plan, annual rate of return on long-term investment period one (as a percent)	7.10%
Defined benefit plan, annual rate of return on long-term investment period two (as a percent)	5.60%
Defined benefit plan, annual rate of return on long-term investment period three (as a percent)	7.80%
Defined benefit plan, annual rate of return on long-term investment period four (as a percent)	8.70%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (as a percent)	60.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (as a percent)	40.00%
U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	8.00%	8.25%	8.25%
2013	$ 31.3
2014	32.4
2015	34.1
2016	35.4
2017	36.8
Years 2018 - 2022	205.5
Weighted-average discount rate	4.00%	4.25%
Non-U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	6.32%	6.34%	6.25%
2013	3.8
2014	3.3
2015	2.2
2016	7.8
2017	1.7
Years 2018 - 2022	$ 17.0
Weighted-average discount rate	3.89%	4.68%