Discontinued operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011
Arbitration charge related to a guarantee			$ 21.0
Arbitration charge after tax	$ (13.0)	$ 13.0	$ 13.0