Inventory, Linefill and Base Gas and Long-term Inventory (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Inventory by category
Inventory	$ 929		$ 891
Linefill and base gas	960		930
Long-term inventory	149		186
Total	2,038		2,007
Inventory-related disclosures
Charge related to the write-down of inventory	24	37
Crude oil
Inventory by category
Inventory	686		304
Linefill and base gas	777		744
Long-term inventory	117		136
Inventory, Volumes (in barrels or in Mcf)	15,351,000		6,465,000
Linefill and base gas, Volumes (in barrels or in Mcf)	12,970,000		11,810,000
Long-term inventory, Volumes (in barrels or in Mcf)	2,646,000		2,582,000
Inventory, Price/Unit of measure (in dollars per unit)	44.69		47.02
Linefill and base gas, Price/Unit of measure (in dollars per unit)	59.91		63.00
Long-term inventory, Price/Unit of measure (in dollars per unit)	44.22		52.67
NGL
Inventory by category
Inventory	154		454
Linefill and base gas	48		52
Long-term inventory	32		50
Inventory, Volumes (in barrels or in Mcf)	7,277,000		13,553,000
Linefill and base gas, Volumes (in barrels or in Mcf)	1,215,000		1,212,000
Long-term inventory, Volumes (in barrels or in Mcf)	1,681,000		1,681,000
Inventory, Price/Unit of measure (in dollars per unit)	21.16		33.50
Linefill and base gas, Price/Unit of measure (in dollars per unit)	39.51		42.90
Long-term inventory, Price/Unit of measure (in dollars per unit)	19.04		29.74
Natural gas
Inventory by category
Inventory	31		102
Linefill and base gas	135		134
Inventory, Volumes (in barrels or in Mcf)	10,965,000		32,317,000
Linefill and base gas, Volumes (in barrels or in Mcf)	28,612,000		28,612,000
Inventory, Price/Unit of measure (in dollars per unit)	2.83		3.16
Linefill and base gas, Price/Unit of measure (in dollars per unit)	4.72		4.68
Other
Inventory by category
Inventory	$ 58		$ 31