Supplemental Guarantor Condensed Consolidating Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 111	$ 115
Receivables trade and other, net	625	588
Inventories	491	477
Other current assets	32	46
TOTAL CURRENT ASSETS	1,259	1,226
NET PROPERTY	481	483
GOODWILL	421	421
OTHER ASSETS	567	596
INVESTMENTS IN SUBSIDIARIES	0	0
TOTAL ASSETS	2,728	2,726
CURRENT LIABILITIES:
Short-term debt	24	94
Accounts and notes payable	691	700
Other current liabilities	296	290
TOTAL CURRENT LIABILITIES	1,011	1,084
LONG-TERM DEBT	734	730
RETIREMENT BENEFITS	238	262
INTERCOMPANY PAYABLE (RECEIVABLE)	0	0
OTHER LIABILITIES	234	332
MEZZANINE EQUITY	1	1
EQUITY ATTRIBUTABLE TO MERITOR, INC.	474	287
NONCONTROLLING INTERESTS	36	30
TOTAL LIABILITIES, MEZZANINE EQUITY AND EQUITY	2,728	2,726
Elims
CURRENT ASSETS:
Cash and cash equivalents	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	(5,148)	(4,438)
TOTAL ASSETS	(5,148)	(4,438)
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	0
EQUITY ATTRIBUTABLE TO MERITOR, INC.	(5,148)	(4,438)
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES, MEZZANINE EQUITY AND EQUITY	(5,148)	(4,438)
Parent | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents	27	24
Receivables trade and other, net	3	2
Inventories	0	0
Other current assets	4	6
TOTAL CURRENT ASSETS	34	32
NET PROPERTY	21	24
GOODWILL	0	0
OTHER ASSETS	147	179
INVESTMENTS IN SUBSIDIARIES	4,188	3,583
TOTAL ASSETS	4,390	3,818
CURRENT LIABILITIES:
Short-term debt	23	47
Accounts and notes payable	54	64
Other current liabilities	144	77
TOTAL CURRENT LIABILITIES	221	188
LONG-TERM DEBT	730	726
RETIREMENT BENEFITS	218	241
INTERCOMPANY PAYABLE (RECEIVABLE)	2,691	2,325
OTHER LIABILITIES	55	50
MEZZANINE EQUITY	1	1
EQUITY ATTRIBUTABLE TO MERITOR, INC.	474	287
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES, MEZZANINE EQUITY AND EQUITY	4,390	3,818
Guarantors | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents	5	6
Receivables trade and other, net	81	62
Inventories	260	242
Other current assets	11	12
TOTAL CURRENT ASSETS	357	322
NET PROPERTY	240	241
GOODWILL	254	250
OTHER ASSETS	189	182
INVESTMENTS IN SUBSIDIARIES	960	855
TOTAL ASSETS	2,000	1,850
CURRENT LIABILITIES:
Short-term debt	0	0
Accounts and notes payable	292	297
Other current liabilities	65	71
TOTAL CURRENT LIABILITIES	357	368
LONG-TERM DEBT	0	0
RETIREMENT BENEFITS	0	0
INTERCOMPANY PAYABLE (RECEIVABLE)	(2,856)	(2,640)
OTHER LIABILITIES	118	124
MEZZANINE EQUITY	0	0
EQUITY ATTRIBUTABLE TO MERITOR, INC.	4,381	3,998
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES, MEZZANINE EQUITY AND EQUITY	2,000	1,850
Non- Guarantors | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents	79	85
Receivables trade and other, net	541	524
Inventories	231	235
Other current assets	17	28
TOTAL CURRENT ASSETS	868	872
NET PROPERTY	220	218
GOODWILL	167	171
OTHER ASSETS	231	235
INVESTMENTS IN SUBSIDIARIES	0	0
TOTAL ASSETS	1,486	1,496
CURRENT LIABILITIES:
Short-term debt	1	47
Accounts and notes payable	345	339
Other current liabilities	87	142
TOTAL CURRENT LIABILITIES	433	528
LONG-TERM DEBT	4	4
RETIREMENT BENEFITS	20	21
INTERCOMPANY PAYABLE (RECEIVABLE)	165	315
OTHER LIABILITIES	61	158
MEZZANINE EQUITY	0	0
EQUITY ATTRIBUTABLE TO MERITOR, INC.	767	440
NONCONTROLLING INTERESTS	36	30
TOTAL LIABILITIES, MEZZANINE EQUITY AND EQUITY	$ 1,486	$ 1,496