Commitments and Contingencies (Details 3) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended	12 Months Ended					3 Months Ended
	Feb. 25, 2013 Litigation CRNF	Mar. 31, 2013 Litigation CRNF	Dec. 31, 2012 Litigation CRNF	Dec. 31, 2011 Litigation CRNF	Dec. 31, 2010 Litigation CRNF	Dec. 31, 2009 Litigation CRNF	Dec. 31, 2008 Litigation CRNF	Mar. 31, 2013 EHS	Mar. 31, 2012 EHS
Commitments and Contingencies
Property tax abatement period		10 years
Increase in property tax expenses			$ 11.3	$ 11.4	$ 11.7	$ 10.7	$ 10.7
Decrease in property tax expenses	10.5
Expenses related to environmental, health and safety (EHS) matters								$ 0	$ 0.2