Contingent Liabilities (Details Textual) (USD $)	84 Months Ended								1 Months Ended
	Dec. 31, 2010	Jun. 30, 2011 Former Operations	Mar. 31, 2008 Environmental Protection Agency	Jun. 30, 2011 Natural gas underground storage facilities	Dec. 31, 2008 Gulf Liquids	Dec. 31, 2006 Gulf Liquids	Jan. 28, 2008 Gulf Liquids Gulsby-Bay	Jan. 28, 2008 Gulf Liquids Gulsby	Feb. 28, 2011 Pending or Threatened Litigation	Jun. 30, 2011 Gas Pipeline
Contingent Liabilities (Textuals) [Abstract]
Accrued environmental loss liabilities		$ 30,000,000		$ 8,000,000						$ 11,000,000
Estimated exposure for actual damages			370,000			68,000,000
Potential interest in addition to actual damages						20,000,000
Possible ultimate judgement in excess of accrual						199,000,000
Litigation award against Gulf Liquids, Damages							4,000,000	11,000,000
Loss contingency accrual reduction					43,000,000
Loss contingency accrued interest reduction					11,000,000
Assertion of Counterclaim									200,000,000
Contingent Liabilities Additional (Textuals) [Abstract]
Deductions used in calculation of royalty payments.	$ 55,000,000