Revenues and Accounts Receivable - Segment Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 7,886	$ 8,792	$ 24,515	$ 25,269
Transportation
Disaggregation of Revenue [Line Items]
Total revenues	196	161	581	458
Facilities
Disaggregation of Revenue [Line Items]
Total revenues	149	149	457	437
Supply and Logistics
Disaggregation of Revenue [Line Items]
Total revenues	7,541	8,482	23,477	24,374
Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,258	9,315	25,624	27,093
Total revenues	8,430	9,270	26,072	26,669
Operating Segments | Transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	590	496	1,685	1,416
Total revenues	597	498	1,712	1,427
Operating Segments | Facilities
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	281	285	843	845
Total revenues	291	289	880	866
Operating Segments | Supply and Logistics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	7,387	8,534	23,096	24,832
Total revenues	7,542	8,483	23,480	24,376
Intersegment
Disaggregation of Revenue [Line Items]
Total revenues	(544)	(478)	(1,557)	(1,400)
Intersegment | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	(278)	(206)	(774)	(619)
Intersegment | Facilities
Disaggregation of Revenue [Line Items]
Total revenues	(142)	(140)	(423)	(429)
Intersegment | Supply and Logistics
Disaggregation of Revenue [Line Items]
Total revenues	(1)	(1)	(3)	(2)
Other | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	172	(45)	448	(424)
Other | Operating Segments | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	7	2	27	11
Other | Operating Segments | Facilities
Disaggregation of Revenue [Line Items]
Total revenues	10	4	37	21
Other | Operating Segments | Supply and Logistics
Disaggregation of Revenue [Line Items]
Total revenues	$ 155	$ (51)	$ 384	$ (456)