Revenues - Contract Assets and Liabilities (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Contract With Customer, Asset And Liability [Line Items]
Revenue recognized	$ 78
Other current assets	320	$ 221
Contract liability, deferred revenue	$ 393	90
General payment terms	P30D
Trade accounts receivable arising from revenues from contracts with customers	$ 2,910	2,584
Other trade accounts receivables and other receivables	3,482	3,709
Impact due to contractual rights of offset with counterparties	(3,438)	(3,264)
Trade accounts receivable and other receivables, net	2,954	3,029
Minimum Volume Commitments
Contract With Customer, Asset And Liability [Line Items]
Contract liability, deferred revenue	42	37
Counterparty deficiencies	62	57
Counterparty deficiencies unbilled and uncollected	20	$ 20
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	157
Contract liability, deferred revenue	$ 159