Revenue Recognition - Receivables and Contract Liabilities (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) term	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Receivables from contracts with customers	$ 12		$ 19
Deferred revenue	0	$ 8	8
Total	853
Less than 1 year	108
Years 2 to 3	216
Years 4 to 5	216
More than 5 years	313
Related Parties
Disaggregation of Revenue [Line Items]
Receivables from contracts with customers	25	21
Deferred revenue	0	3	3
Third Parties
Disaggregation of Revenue [Line Items]
Receivables from contracts with customers	13	$ 19
Deferred revenue	$ 0		$ 8
Transportation Services Operating Leases, Five Year Terms
Disaggregation of Revenue [Line Items]
Initial term	10 years
Number of additional terms | term	2
Additional term	5 years
Transportation Services Operating Leases, One Year Terms
Disaggregation of Revenue [Line Items]
Initial term	10 years
Number of additional terms | term	10
Additional term	1 year
Transportation Services Operating Leases
Disaggregation of Revenue [Line Items]
Initial term	10 years