CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) shares in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Sales	$ 4,388,000,000	$ 4,178,000,000	$ 3,347,000,000
Cost of sales	(3,748,000,000)	(3,553,000,000)	(2,850,000,000)
GROSS MARGIN	640,000,000	625,000,000	497,000,000
Selling, general and administrative	(256,000,000)	(313,000,000)	(266,000,000)
Restructuring costs	(8,000,000)	(6,000,000)	(6,000,000)
Other operating expense, net	(13,000,000)	(14,000,000)	(7,000,000)
OPERATING INCOME (LOSS)	363,000,000	292,000,000	218,000,000
Other income (expense), net	40,000,000	26,000,000	(9,000,000)
Gain on sale of equity investment	0	0	243,000,000
Equity in earnings of affiliates	31,000,000	27,000,000	48,000,000
Interest expense, net	(57,000,000)	(67,000,000)	(119,000,000)
INCOME (LOSS) BEFORE INCOME TAXES	377,000,000	278,000,000	381,000,000
Provision for income taxes	(82,000,000)	(149,000,000)	(52,000,000)
INCOME FROM CONTINUING OPERATIONS	295,000,000	129,000,000	329,000,000
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax	1,000,000	(3,000,000)	(1,000,000)
NET INCOME	296,000,000	126,000,000	328,000,000
Less: Net income attributable to noncontrolling interests	(5,000,000)	(9,000,000)	(4,000,000)
NET INCOME ATTRIBUTABLE TO MERITOR, INC.	291,000,000	117,000,000	324,000,000
NET INCOME ATTRIBUTABLE TO MERITOR, INC.
Net income from continuing operations	290,000,000	120,000,000	325,000,000
Income (loss) from discontinued operations	1,000,000	(3,000,000)	(1,000,000)
Net income	$ 291,000,000	$ 117,000,000	$ 324,000,000
BASIC EARNINGS (LOSS) PER SHARE
Basic earnings (loss) per share from continuing operations (in dollars per share)	$ 3.49	$ 1.37	$ 3.69
Basic earnings (loss) per share from discontinued operations (in dollars per share)	0.01	(0.03)	(0.01)
Basic earnings (loss) per share (in dollars per share)	3.50	1.34	3.68
DILUTED EARNINGS (LOSS) PER SHARE
Diluted earnings (loss) per share from continuing operations (in dollars per share)	3.36	1.31	3.60
Diluted earnings (loss) per share from discontinued operations (in dollars per share)	0.01	(0.03)	(0.01)
Diluted earnings (loss) per share (in dollars per share)	$ 3.37	$ 1.28	$ 3.59
Basic average common shares outstanding (in shares)	83.2	87.5	88.0
Diluted average common shares outstanding (in shares)	86.3	91.2	90.2