Revenues and Accounts Receivable - Narrative (Details) $ in Millions	1 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($) $ / bbl	Oct. 31, 2018 $ / bbl	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Contract With Customer, Asset And Liability [Line Items]
Other current assets	$ 373		$ 373	$ 373	$ 221
Contract liability, deferred revenue	$ 338		$ 338	338	90
Decrease in NYMEX WTI oil price, percentage			44.00%
NYMEX WTI oil price (in dollars per barrel) | $ / bbl	42.53	76.41
Advance cash payments received from third parties to mitigate credit risk	$ 140		$ 140	140	117
Standby letters of credit	117		117	$ 117	54
Substantially all trade accounts receivable, net, maximum age of balances past their scheduled invoice date				30 years
Allowance for doubtful accounts receivable					3
General payment terms				P30D
Crude Oil Sales Agreements Entered Into In Conjunction WIth Storage Arrangements And Future Inventory Exchanges
Contract With Customer, Asset And Liability [Line Items]
Other current assets	115		115	$ 115
Contract liability, deferred revenue	116		116	116
Minimum Volume Commitments
Contract With Customer, Asset And Liability [Line Items]
Counterparty deficiencies	62		62	62	57
Contract liability, deferred revenue	40		40	40	37
Counterparty deficiencies unbilled and uncollected	$ 22		$ 22	$ 22	$ 20