Supplemental Guarantor Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Condensed Statement of Income Captions [Line Items]
Net income (loss)	$ 23	$ 32	$ 39	$ 59
Other comprehensive income (loss)	32	18	14	24
Total comprehensive income	55	50	53	83
Less: Comprehensive income attributable to noncontrolling interests	(2)	0	(1)	(1)
Comprehensive income attributable to Meritor, Inc.	53	50	52	82
Elims
Condensed Statement of Income Captions [Line Items]
Net income (loss)	(66)	(51)	(158)	(166)
Other comprehensive income (loss)	(19)	(13)	4	(10)
Total comprehensive income	(85)	(64)	(154)	(176)
Less: Comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Meritor, Inc.	(85)	(64)	(154)	(176)
Parent | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income (loss)	22	32	37	58
Other comprehensive income (loss)	30	18	14	24
Total comprehensive income	52	50	51	82
Less: Comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Meritor, Inc.	52	50	51	82
Guarantors | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income (loss)	47	54	110	141
Other comprehensive income (loss)	0	23	2	12
Total comprehensive income	47	77	112	153
Less: Comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Meritor, Inc.	47	77	112	153
Non- Guarantors | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income (loss)	20	(3)	50	26
Other comprehensive income (loss)	21	(10)	(6)	(2)
Total comprehensive income	41	(13)	44	24
Less: Comprehensive income attributable to noncontrolling interests	(2)	0	(1)	(1)
Comprehensive income attributable to Meritor, Inc.	$ 39	$ (13)	$ 43	$ 23