Commitments And Contingencies (Details) (USD $)	3 Months Ended		6 Months Ended							0 Months Ended	1 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Y	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 TCEQ Fees [Member]	Jun. 30, 2012 TCEQ Fees [Member] Minimum [Member]	Jun. 30, 2012 TCEQ Fees [Member] Maximum [Member]	Jun. 30, 2012 Osage Complaint [Member]	Nov. 04, 2011 MF Global Holdings Ltd. Bankruptcy [Member]	Jul. 31, 2012 MF Global Holdings Ltd. Bankruptcy [Member]	Jun. 30, 2012 Other Accounts Receivables [Member]	Dec. 31, 2011 Other Accounts Receivables [Member]	Jun. 30, 2012 Long-Term Receivables [Member]	Dec. 31, 2011 Long-Term Receivables [Member]
Commitments And Contingencies [Line Items]
Estimated fees for excess emissions, minimum							$ 6,400,000		$ 0
Estimated fees for excess emissions, maximum								13,700,000	5,500,000
Estimated fees for excess emissions, accrual						8,900,000
Interest in equity method investment									50.00%
Amount owed on transfer of existing trading positions										29,400,000
Amount received from existing trading positions										21,200,000	2,400,000
Remaining amount owed										8,200,000	5,800,000
Liabilities recognized for estimated environmental costs	43,600,000		43,600,000		49,600,000
Estimated environmental liabilities, years			10
Environmental expenses	100,000	8,600,000	2,700,000	12,500,000
Receivables from insurance carriers related to environmental matters	7,800,000		7,800,000		7,700,000							4,700,000	5,200,000	3,100,000	2,500,000
Unrecognized product overages	$ 2,800,000		$ 2,800,000