CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Sales	$ 903	$ 699
Cost of sales	(763)	(610)
GROSS MARGIN	140	89
Selling, general and administrative	(67)	(53)
Restructuring costs	(2)	0
Other operating expense, net	(1)	(3)
OPERATING INCOME (LOSS)	70	33
Other expense, net	(1)	0
Equity in earnings of affiliates	5	10
Interest expense, net	(24)	(21)
INCOME (LOSS) BEFORE INCOME TAXES	50	22
Provision for income taxes	(83)	(6)
INCOME (LOSS) FROM CONTINUING OPERATIONS	(33)	16
LOSS FROM DISCONTINUED OPERATIONS, net of tax	(1)	0
NET INCOME (LOSS)	(34)	16
Less: Net income attributable to noncontrolling interests	(2)	(1)
NET INCOME (LOSS) ATTRIBUTABLE TO MERITOR, INC.	(36)	15
NET INCOME (LOSS) ATTRIBUTABLE TO MERITOR, INC.
Net income (loss) from continuing operations	(35)	15
Loss from discontinued operations	(1)	0
NET INCOME (LOSS) ATTRIBUTABLE TO MERITOR, INC.	$ (36)	$ 15
BASIC EARNINGS (LOSS) PER SHARE
Continuing operations (in usd per share)	$ (0.40)	$ 0.17
Discontinued operations (in usd per share)	(0.01)	0.00
Basic earnings (loss) per share (in usd per share)	(0.41)	0.17
DILUTED EARNINGS (LOSS) PER SHARE
Continuing operations (in usd per share)	(0.40)	0.17
Discontinued operations (in usd per share)	(0.01)	0.00
Diluted earnings (loss) per share (in usd per share)	$ (0.41)	$ 0.17
Basic average common shares outstanding (in shares)	88.6	87.1
Diluted average common shares outstanding (in shares)	88.6	88.5