Environmental (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Loss Contingencies [Line Items]
Environmental remediation costs	$ 46.1	$ 14.0	$ (0.6)
Accrued environmental liability	88.9	42.2
Other long-term liabilities
Loss Contingencies [Line Items]
Accrued environmental liability	72.6	31.7
Frontier [Member]
Loss Contingencies [Line Items]
Accrued environmental liability		$ 15.6