Inventory, Linefill and Base Gas and Long-term Inventory (Details) bbl in Thousands, Mcf in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / bbl $ / Mcf bbl Mcf	Dec. 31, 2019 USD ($) $ / bbl $ / Mcf Mcf bbl	Dec. 31, 2018 USD ($)
Inventory-related disclosures
Charge related to the write-down of inventory	$ 233	$ 11	$ 8
Charge related to the write-down of inventory, long-term inventory	40
Inventory by category
Inventory	647	604
Linefill and base gas	982	981
Long-term inventory	130	182
Total	$ 1,759	$ 1,767
Crude oil
Inventory by category
Inventory, Volumes (in barrels or in Mcf) | bbl	13,450	8,613
Linefill and base gas, Volumes (in barrels or in Mcf) | bbl	14,669	14,316
Long-term inventory, Volumes (in barrels or in Mcf) | bbl	2,499	2,598
Inventory	$ 441	$ 450
Linefill and base gas	828	826
Long-term inventory	$ 111	$ 152
Inventory, Price/Unit of measure (in dollars per unit) | $ / bbl	32.79	52.25
Linefill and base gas, Price/Unit of measure (in dollars per unit) | $ / bbl	56.45	57.70
Long-term inventory, Price/Unit of measure (in dollars per unit) | $ / bbl	44.42	58.51
NGL
Inventory by category
Inventory, Volumes (in barrels or in Mcf) | bbl	12,302	7,574
Linefill and base gas, Volumes (in barrels or in Mcf) | bbl	1,640	1,701
Long-term inventory, Volumes (in barrels or in Mcf) | bbl	1,185	1,707
Inventory	$ 199	$ 142
Linefill and base gas	44	47
Long-term inventory	$ 19	$ 30
Inventory, Price/Unit of measure (in dollars per unit) | $ / bbl	16.18	18.75
Linefill and base gas, Price/Unit of measure (in dollars per unit) | $ / bbl	26.83	27.63
Long-term inventory, Price/Unit of measure (in dollars per unit) | $ / bbl	16.03	17.57
Natural gas
Inventory by category
Linefill and base gas, Volumes (in barrels or in Mcf) | Mcf	25,576	24,976
Linefill and base gas	$ 110	$ 108
Linefill and base gas, Price/Unit of measure (in dollars per unit) | $ / Mcf	4.30	4.32
Other
Inventory by category
Inventory	$ 7	$ 12