Net Gains on Sales of Fixed Assets Net Gains on Sales of Fixed Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Property, Plant and Equipment [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	$ 109	$ 0	$ 158	$ 2
Natural Gas Gathering Systems And Treating Plants [Member]
Property, Plant and Equipment [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	109	0	179	1
Drilling Rigs And Equipment [Member]
Property, Plant and Equipment [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	0	(1)	(1)	(2)
Land and Building [Member]
Property, Plant and Equipment [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	(1)	0	(23)	0
Other Assets
Property, Plant and Equipment [Line Items]
Gain (Loss) on Sale of Property Plant Equipment	$ 1	$ 1	$ 3	$ 3