CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Sales	$ 1,038	$ 903
Cost of sales	(897)	(771)
GROSS MARGIN	141	132
Selling, general and administrative	(34)	(67)
Restructuring costs	0	(2)
Other operating expense, net	0	(1)
OPERATING INCOME (LOSS)	107	62
Other income, net	11	7
Equity in earnings of affiliates	9	5
Interest income (expense), net	(14)	(24)
INCOME (LOSS) BEFORE INCOME TAXES	113	50
Benefit (Provision) for income taxes	(21)	(83)
INCOME (LOSS) FROM CONTINUING OPERATIONS	92	(33)
LOSS FROM DISCONTINUED OPERATIONS, net of tax	0	(1)
NET INCOME (LOSS)	92	(34)
Less: Net income attributable to noncontrolling interests	(2)	(2)
NET INCOME (LOSS) ATTRIBUTABLE TO MERITOR, INC.	90	(36)
NET INCOME (LOSS) ATTRIBUTABLE TO MERITOR, INC.
Net income (loss) from continuing operations	90	(35)
Loss from discontinued operations	0	(1)
NET INCOME (LOSS) ATTRIBUTABLE TO MERITOR, INC.	$ 90	$ (36)
BASIC EARNINGS (LOSS) PER SHARE
Continuing operations (in usd per share)	$ 1.06	$ (0.40)
Discontinued operations (in usd per share)	0.00	(0.01)
Basic earnings per share (in usd per share)	1.06	(0.41)
DILUTED EARNINGS (LOSS) PER SHARE
Continuing operations (in usd per share)	1.03	(0.40)
Discontinued operations (in usd per share)	0.00	(0.01)
Diluted earnings per share (in usd per share)	$ 1.03	$ (0.41)
Basic average common shares outstanding (in shares)	84.8	88.6
Diluted average common shares outstanding (in shares)	87.5	88.6