Revenues and Accounts Receivable - Disaggregation of Revenue (Details) - Operating Segments - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 6,324	$ 8,258	$ 18,725	$ 25,624
Supply and Logistics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,574	7,387	16,380	23,096
Supply and Logistics | Crude oil transactions
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,394	7,185	15,644	21,716
Supply and Logistics | NGL and other transactions
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	180	202	736	1,380
Transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	488	590	1,514	1,685
Transportation | Total tariff activities
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	468	557	1,437	1,579
Transportation | Crude oil pipelines
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	442	532	1,360	1,504
Transportation | NGL pipelines
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	26	25	77	75
Transportation | Trucking
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	20	33	77	106
Facilities
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	262	281	831	843
Facilities | Crude oil, NGL and other terminalling and storage
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	178	174	536	523
Facilities | NGL and natural gas processing and fractionation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	76	87	265	262
Facilities | Rail load / unload
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 8	$ 20	$ 30	$ 58