Reportable Segments (Schedule of Capital Expenditures) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Capital expenditures	$ 58	$ 46	$ 102	$ 86
IMTT
Segment Reporting Information [Line Items]
Capital expenditures	38	15	64	24
Atlantic Aviation
Segment Reporting Information [Line Items]
Capital expenditures	14	17	27	36
MIC Hawaii
Segment Reporting Information [Line Items]
Capital expenditures	5	5	10	11
Corporate and Other
Segment Reporting Information [Line Items]
Capital expenditures	$ 1	$ 9	$ 1	$ 15