Inventory, Linefill and Base Gas and Long-term Inventory (Details) bbl in Thousands, Mcf in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) $ / bbl $ / Mcf bbl Mcf	Dec. 31, 2019 USD ($) $ / bbl $ / Mcf bbl Mcf
Inventory by category
Inventory	$ 181	$ 604
Linefill and base gas	955	981
Long-term inventory	73	182
Total	1,209	$ 1,767
Charge related to the write-down of inventory	232
Charge related to the write-down of inventory, long-term inventory	$ 40
Crude oil
Inventory by category
Inventory, Volumes (in barrels or in Mcf) | bbl	7,168	8,613
Linefill and base gas, Volumes (in barrels or in Mcf) | bbl	14,251	14,316
Long-term inventory, Volumes (in barrels or in Mcf) | bbl	2,789	2,598
Inventory	$ 128	$ 450
Linefill and base gas	804	826
Long-term inventory	$ 55	$ 152
Inventory (Price/Unit of measure) | $ / bbl	17.86	52.25
Linefill and base gas (Price/Unit of measure) | $ / bbl	56.42	57.70
Long-term inventory (Price/Unit of measure) | $ / bbl	19.72	58.51
NGL
Inventory by category
Inventory, Volumes (in barrels or in Mcf) | bbl	3,992	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	1,579	1,707
Inventory	$ 42	$ 142
Linefill and base gas	41	47
Long-term inventory	$ 18	$ 30
Inventory (Price/Unit of measure) | $ / bbl	10.52	18.75
Linefill and base gas (Price/Unit of measure) | $ / bbl	25.00	27.63
Long-term inventory (Price/Unit of measure) | $ / bbl	11.40	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) | $ / Mcf	4.30	4.32
Other
Inventory by category
Inventory	$ 11	$ 12