Discontinued Operations and Dispositions (Statement Of Operations) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Product revenue		$ 18	$ 42	$ 34	$ 77
Cost of product sales		(3)	(6)	(6)	(12)
Selling, general & administrative expenses		(3)	(7)	(7)	(14)
Depreciation and amortization		0	(15)	0	(30)
Interest expense, net		(7)	(5)	(12)	(6)
Other expense, net		0	0	(1)	0
Net income from discontinued operations before income taxes	[1]	5	9	8	15
(Provision) benefit for income taxes	[1]	(2)	0	0	1
Net income from discontinued operations	[1]	3	9	8	16
Less: net loss attributable to noncontrolling interests		(2)	(2)	(3)	(32)
Net income from discontinued operations attributable to MIC		$ 5	$ 11	$ 11	$ 48

[1] See Note 3, “Discontinued Operations and Dispositions”, for discussions on businesses classified as held for sale.