Supplemental Guarantor Condensed Consolidating Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions		Mar. 31, 2017		Sep. 30, 2016		Mar. 31, 2016	Sep. 30, 2015
CURRENT ASSETS:
Cash and cash equivalents		$ 138	[1]	$ 160	[1]	$ 94	$ 193
Receivables trade and other, net	[1]	442		396
Inventories	[1]	338		316
Other current assets		42		33
TOTAL CURRENT ASSETS		960		905
NET PROPERTY	[1]	430		439
GOODWILL	[1]	385		390
OTHER ASSETS		761		760
INVESTMENTS IN SUBSIDIARIES		0		0
TOTAL ASSETS		2,536		2,494
CURRENT LIABILITIES:
Short-term debt		132		14
Accounts and notes payable	[1]	528		475
Other current liabilities		245		268
TOTAL CURRENT LIABILITIES		905		757
LONG-TERM DEBT		857		982
RETIREMENT BENEFITS		680		703
INTERCOMPANY PAYABLE (RECEIVABLE)		0		0
OTHER LIABILITIES		219		238
MEZZANINE EQUITY		13		0
EQUITY (DEFICIT) ATTRIBUTABLE TO MERITOR, INC.		(163)		(211)
NONCONTROLLING INTERESTS	[1]	25		25
TOTAL LIABILITIES, MEZZANINE EQUITY AND DEFICIT		2,536		2,494
ASSETS, LIABILITIES, AND EQUITY HELD-FOR-SALE
Cash and cash equivalents		1		1
Receivables, trade and other, net		8		8
Inventories		1		1
Goodwill		1
Net property				3
Accounts and notes payable		6		5
Noncontrolling interests		2		3
Elims
CURRENT ASSETS:
Cash and cash equivalents		0		0		0	0
Receivables trade and other, net		0		0
Inventories		0		0
Other current assets		0		0
TOTAL CURRENT ASSETS		0		0
NET PROPERTY		0		0
GOODWILL		0		0
OTHER ASSETS		0		0
INVESTMENTS IN SUBSIDIARIES		(3,442)		(3,254)
TOTAL ASSETS		(3,442)		(3,254)
CURRENT LIABILITIES:
Short-term debt		0		0
Accounts and notes payable		0		0
Other current liabilities		0		0
TOTAL CURRENT LIABILITIES		0		0
LONG-TERM DEBT		0		0
RETIREMENT BENEFITS		0		0
INTERCOMPANY PAYABLE (RECEIVABLE)		0		0
OTHER LIABILITIES		0		0
MEZZANINE EQUITY		0
EQUITY (DEFICIT) ATTRIBUTABLE TO MERITOR, INC.		(3,442)		(3,254)
NONCONTROLLING INTERESTS		0		0
TOTAL LIABILITIES, MEZZANINE EQUITY AND DEFICIT		(3,442)		(3,254)
Parent | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents		67		90		24	73
Receivables trade and other, net		1		1
Inventories		0		0
Other current assets		7		5
TOTAL CURRENT ASSETS		75		96
NET PROPERTY		22		22
GOODWILL		0		0
OTHER ASSETS		443		447
INVESTMENTS IN SUBSIDIARIES		2,728		2,575
TOTAL ASSETS		3,268		3,140
CURRENT LIABILITIES:
Short-term debt		128		1
Accounts and notes payable		40		42
Other current liabilities		85		90
TOTAL CURRENT LIABILITIES		253		133
LONG-TERM DEBT		848		971
RETIREMENT BENEFITS		659		680
INTERCOMPANY PAYABLE (RECEIVABLE)		1,629		1,534
OTHER LIABILITIES		29		34
MEZZANINE EQUITY		13
EQUITY (DEFICIT) ATTRIBUTABLE TO MERITOR, INC.		(163)		(212)
NONCONTROLLING INTERESTS		0		0
TOTAL LIABILITIES, MEZZANINE EQUITY AND DEFICIT		3,268		3,140
Guarantors | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents		4		4		5	6
Receivables trade and other, net		57		39
Inventories		151		143
Other current assets		14		12
TOTAL CURRENT ASSETS		226		198
NET PROPERTY		202		198
GOODWILL		219		219
OTHER ASSETS		130		132
INVESTMENTS IN SUBSIDIARIES		714		679
TOTAL ASSETS		1,491		1,426
CURRENT LIABILITIES:
Short-term debt		3		4
Accounts and notes payable		198		172
Other current liabilities		73		74
TOTAL CURRENT LIABILITIES		274		250
LONG-TERM DEBT		1		3
RETIREMENT BENEFITS		0		0
INTERCOMPANY PAYABLE (RECEIVABLE)		(1,859)		(1,768)
OTHER LIABILITIES		149		162
MEZZANINE EQUITY		0
EQUITY (DEFICIT) ATTRIBUTABLE TO MERITOR, INC.		2,926		2,779
NONCONTROLLING INTERESTS		0		0
TOTAL LIABILITIES, MEZZANINE EQUITY AND DEFICIT		1,491		1,426
Non- Guarantors | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents		67		66		$ 65	$ 114
Receivables trade and other, net		384		356
Inventories		187		173
Other current assets		21		16
TOTAL CURRENT ASSETS		659		611
NET PROPERTY		206		219
GOODWILL		166		171
OTHER ASSETS		188		181
INVESTMENTS IN SUBSIDIARIES		0		0
TOTAL ASSETS		1,219		1,182
CURRENT LIABILITIES:
Short-term debt		1		9
Accounts and notes payable		290		261
Other current liabilities		87		104
TOTAL CURRENT LIABILITIES		378		374
LONG-TERM DEBT		8		8
RETIREMENT BENEFITS		21		23
INTERCOMPANY PAYABLE (RECEIVABLE)		230		234
OTHER LIABILITIES		41		42
MEZZANINE EQUITY		0
EQUITY (DEFICIT) ATTRIBUTABLE TO MERITOR, INC.		516		476
NONCONTROLLING INTERESTS		25		25
TOTAL LIABILITIES, MEZZANINE EQUITY AND DEFICIT		$ 1,219		$ 1,182

[1] As of March 31, 2017, Assets and Liabilities held for sale were: (i) $1 million Cash and cash equivalents; (ii) $8 million Receivables, trade and other, net; (iii) $1 million Inventories; (iv) $1 million Goodwill; (v) $6 million Accounts and notes payable; and (vi) $2 million Noncontrolling interests. As of September 30, 2016, Assets and Liabilities held for sale were: (i) $1 million Cash and cash equivalents; (ii) $8 million Receivables, trade and other, net; (iii) $1 million Inventories; (iv) $3 million Net property; (v) $5 million Accounts and notes payable; and (vi) $3 million Noncontrolling interests.