Revenues and Accounts Receivable - Segment Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 8,383	$ 8,269
Transportation
Disaggregation of Revenue [Line Items]
Total revenues	137	187
Facilities
Disaggregation of Revenue [Line Items]
Total revenues	163	175
Supply and Logistics
Disaggregation of Revenue [Line Items]
Total revenues	8,083	7,907
Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9,095	8,628
Total revenues	8,841	8,800
Operating Segments | Transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	446	573
Total revenues	487	579
Operating Segments | Facilities
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	254	305
Total revenues	271	313
Operating Segments | Supply and Logistics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,395	7,750
Total revenues	8,083	7,908
Intersegment
Disaggregation of Revenue [Line Items]
Total revenues	(458)	(531)
Intersegment | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	(253)	(282)
Intersegment | Facilities
Disaggregation of Revenue [Line Items]
Total revenues	(108)	(138)
Intersegment | Supply and Logistics
Disaggregation of Revenue [Line Items]
Total revenues		(1)
Other | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	(254)	172
Other | Operating Segments | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	41	6
Other | Operating Segments | Facilities
Disaggregation of Revenue [Line Items]
Total revenues	17	8
Other | Operating Segments | Supply and Logistics
Disaggregation of Revenue [Line Items]
Total revenues	$ (312)	$ 158