Environmental (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Loss Contingencies [Line Items]
Environmental remediation costs	$ 1.0	$ 0.1	$ 15.2	$ 0.1
Accrued environmental liability	61.4		61.4		42.2
Other Long-Term Liabilities [Member]
Loss Contingencies [Line Items]
Accrued environmental liability	48.7		48.7		31.7
Frontier [Member]
Loss Contingencies [Line Items]
Accrued environmental liability		$ 15.6		$ 15.6