Commitments And Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Boe years	Sep. 30, 2010	Dec. 31, 2010
Commitments And Contingencies [Line Items]
Estimated fees for excess emissions, not accrued			$ 6.4
Fees for excess emissions accrued, current			4.8
Fees for excess emissions accrued, non-current	0.6
Fees for excess emissions accrued, long-term			1.6
Liabilities recognized for estimated environmental costs	43.4		43.4		32.8
Estimated environmental liabilities, years			10
Environmental expense	3.6	5.1	16.1	10.2
Receivables from insurance carriers related to environmental matters	5.3		5.3		2.2
Other accounts receivable	1.4		1.4		1.0
Long-term receivables	3.9		3.9		1.2
Unrecognized product overages	3.8		3.8
Maximum [Member]
Commitments And Contingencies [Line Items]
Estimated fees for excess emissions, not accrued			13.7
Minimum [Member]
Commitments And Contingencies [Line Items]
Estimated fees for excess emissions, not accrued			$ 6.4