Intangible Assets and Goodwill (Schedule of Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Beginning balance	$ 2,043
Accumulated impairment charges		$ (126)
Other		(3)
Goodwill acquired	1	2,172
Ending balance	2,044	2,043
IMTT
Goodwill [Line Items]
Beginning balance	1,428
Accumulated impairment charges		0
Other		(2)
Goodwill acquired	0	1,430
Ending balance	1,428	1,428
Atlantic Aviation
Goodwill [Line Items]
Beginning balance	495
Accumulated impairment charges		(123)
Other		(1)
Goodwill acquired	1	619
Ending balance	496	495
MIC Hawaii
Goodwill [Line Items]
Beginning balance	120
Accumulated impairment charges		(3)
Other		0
Goodwill acquired	0	123
Ending balance	$ 120	$ 120