Inventory, Linefill, Base Gas and Long-term Inventory (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Inventory by category
Inventory	$ 1,320		$ 1,320		$ 978
Linefill and base gas	714		714		564
Long-term inventory	287		287		135
Total	2,321		2,321		1,677
Inventory-related disclosures
Ratio of Mcf of natural gas to crude Btu	6		6		6
Non-cash charges related to the write-down of inventory	7	121	128	3
Crude oil
Inventory by category
Inventory	650		650		483
Linefill and base gas	582		582		514
Long-term inventory	143		143		127
Inventory, Volumes (in barrels or in Mcf)	7,122,000		7,122,000		5,361,000
Linefill and base gas, Volumes (in barrels or in Mcf)	9,882,000		9,882,000		9,366,000
Long-term inventory, Volumes (in barrels or cubic feet)	1,916,000		1,916,000		1,714,000
Inventory, Price/Unit of measure (in dollars per unit)	91.27		91.27		90.10
Linefill and base gas, Price/Unit of measure (in dollars per unit)	58.89		58.89		54.88
Long-term inventory, Price/Unit of measure (in dollars per unit)	74.63		74.63		74.10
NGL
Inventory by category
Inventory	604		604		438
Linefill and base gas	81		81		2
Long-term inventory	144		144		8
Inventory, Volumes (in barrels or in Mcf)	14,683,000		14,683,000		6,885,000
Linefill and base gas, Volumes (in barrels or in Mcf)	1,689,000		1,689,000		31,000
Long-term inventory, Volumes (in barrels or cubic feet)	3,620,000		3,620,000		150,000
Inventory, Price/Unit of measure (in dollars per unit)	41.14		41.14		63.62
Linefill and base gas, Price/Unit of measure (in dollars per unit)	47.96		47.96		64.52
Long-term inventory, Price/Unit of measure (in dollars per unit)	39.78		39.78		53.33
Natural gas
Inventory by category
Inventory	51		51		51
Linefill and base gas	51		51		48
Inventory, Volumes (in barrels or in Mcf)	21,800,000		21,800,000		16,170,000
Linefill and base gas, Volumes (in barrels or in Mcf)	15,005,000		15,005,000		14,105,000
Inventory, Price/Unit of measure (in dollars per unit)	2.34		2.34		3.15
Linefill and base gas, Price/Unit of measure (in dollars per unit)	3.40		3.40		3.40
Inventory-related disclosures
Number used to divide into natural gas volumes to convert to barrels	6		6		6
Other
Inventory by category
Inventory	$ 15		$ 15		$ 6