Gains (Losses) on Sales and Impairment of Fixed Assets and Other Gains (Losses) on Sales or Impairments of Fixed Assets and Other Sales Table (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	$ 267	$ 437	$ 137
Natural Gas Gathering Systems And Treating Plants
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	286	440	139
Drilling Rigs And Equipment
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	(10)	(1)	(1)
Land and Building
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	(7)	(2)	(3)
Other Assets
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	$ (2)	$ 0	$ 2