Income per Share (Schedule of Reconciliation) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income from continuing operations attributable to MIC	$ 16	$ 15	$ 6	$ 64	$ (1)	$ 2	$ 27	$ 40	$ 101	$ 68	$ 434
Diluted net income from continuing operations attributable to MIC									101	68	450
Basic and diluted net income from discontinued operations attributable to MIC	$ (2)	$ 46	$ 5	$ 6	$ 1	$ 20	$ 11	$ 37	$ 55	$ 69	$ 17
Denominator:
Weighted average number of shares outstanding: basic (in shares)									86,178,212	85,233,989	83,204,404
Dilutive effect of restricted stock unit grants (in shares)									26,089	15,876	9,495
Weighted average number of shares outstanding: diluted (in shares)									86,204,301	85,249,865	91,073,362
Income per share:
Basic income per share from continuing operations attributable to MIC (in dollars per share)	$ 0.18	$ 0.18	$ 0.07	$ 0.75	$ (0.01)	$ 0.02	$ 0.32	$ 0.47	$ 1.17	$ 0.80	$ 5.22
Basic income per share from discontinued operations attributable to MIC (in dollars per share)	(0.02)	0.53	0.06	0.07	0	0.23	0.13	0.44	0.65	0.80	0.20
Basic income per share attributable to MIC (in dollars per share)	0.16	0.71	0.13	0.82	(0.01)	0.25	0.45	0.91	1.82	1.60	5.42
Diluted income per share from continuing operations attributable to MIC (in dollars per share)	0.18	0.18	0.07	0.73	(0.01)	0.02	0.32	0.47	1.17	0.80	4.94
Diluted income per share from discontinued operations attributable to MIC (in dollars per share)	(0.02)	0.53	0.06	0.06	0	0.23	0.13	0.44	0.65	0.80	0.19
Diluted income per share attributable to MIC (in dollars per share)	$ 0.16	$ 0.71	$ 0.13	$ 0.79	$ (0.01)	$ 0.25	$ 0.45	$ 0.91	$ 1.82	$ 1.60	$ 5.13
2.875% Convertible Senior Notes July 2019
Numerator:
Interest expense attributable to convertible Senior Notes, net of taxes									$ 0	$ 0	$ 8
Denominator:
Dilutive effect of convertible Senior Notes (in shares)									0	0	4,252,609
Income per share:
Interest rate	2.875%								2.875%
2.00% Convertible Senior Notes October 2023
Numerator:
Interest expense attributable to convertible Senior Notes, net of taxes									$ 0	$ 0	$ 8
Denominator:
Dilutive effect of convertible Senior Notes (in shares)									0	0	3,606,854
Income per share:
Interest rate	2.00%								2.00%