Supplemental Guarantor Condensed Consolidating Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 508	$ 108
Receivables trade and other, net	466	551
Inventories	529	526
Other current assets	35	31
TOTAL CURRENT ASSETS	1,538	1,216
NET PROPERTY	509	515
GOODWILL	500	478
OTHER ASSETS	678	606
INVESTMENTS IN SUBSIDIARIES	0	0
TOTAL ASSETS	3,225	2,815
CURRENT LIABILITIES:
Short-term debt	138	41
Accounts and notes payable	541	610
Other current liabilities	257	285
TOTAL CURRENT LIABILITIES	936	936
LONG-TERM DEBT	1,203	902
RETIREMENT BENEFITS	315	336
INTERCOMPANY PAYABLE (RECEIVABLE)	0	0
OTHER LIABILITIES	347	226
EQUITY ATTRIBUTABLE TO MERITOR, INC.	392	385
NONCONTROLLING INTERESTS	32	30
TOTAL LIABILITIES AND EQUITY	3,225	2,815
Eliminations
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	(5,419)	(5,331)
TOTAL ASSETS	(5,419)	(5,331)
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
EQUITY ATTRIBUTABLE TO MERITOR, INC.	(5,419)	(5,331)
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND EQUITY	(5,419)	(5,331)
Parent | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents	351	4
Receivables trade and other, net	0	3
Inventories	0	0
Other current assets	6	6
TOTAL CURRENT ASSETS	357	13
NET PROPERTY	21	21
GOODWILL	0	0
OTHER ASSETS	177	170
INVESTMENTS IN SUBSIDIARIES	4,531	4,432
TOTAL ASSETS	5,086	4,636
CURRENT LIABILITIES:
Short-term debt	33	32
Accounts and notes payable	50	53
Other current liabilities	68	77
TOTAL CURRENT LIABILITIES	151	162
LONG-TERM DEBT	1,200	898
RETIREMENT BENEFITS	291	312
INTERCOMPANY PAYABLE (RECEIVABLE)	2,932	2,833
OTHER LIABILITIES	120	46
EQUITY ATTRIBUTABLE TO MERITOR, INC.	392	385
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND EQUITY	5,086	4,636
Guarantors | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents	4	4
Receivables trade and other, net	78	92
Inventories	297	292
Other current assets	10	10
TOTAL CURRENT ASSETS	389	398
NET PROPERTY	265	260
GOODWILL	360	337
OTHER ASSETS	239	225
INVESTMENTS IN SUBSIDIARIES	888	899
TOTAL ASSETS	2,141	2,119
CURRENT LIABILITIES:
Short-term debt	0	0
Accounts and notes payable	226	283
Other current liabilities	90	109
TOTAL CURRENT LIABILITIES	316	392
LONG-TERM DEBT	0	0
RETIREMENT BENEFITS	1	1
INTERCOMPANY PAYABLE (RECEIVABLE)	(3,030)	(3,005)
OTHER LIABILITIES	124	112
EQUITY ATTRIBUTABLE TO MERITOR, INC.	4,730	4,619
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND EQUITY	2,141	2,119
Non- Guarantors | Reportable Legal Entities
CURRENT ASSETS:
Cash and cash equivalents	153	100
Receivables trade and other, net	388	456
Inventories	232	234
Other current assets	19	15
TOTAL CURRENT ASSETS	792	805
NET PROPERTY	223	234
GOODWILL	140	141
OTHER ASSETS	262	211
INVESTMENTS IN SUBSIDIARIES	0	0
TOTAL ASSETS	1,417	1,391
CURRENT LIABILITIES:
Short-term debt	105	9
Accounts and notes payable	265	274
Other current liabilities	99	99
TOTAL CURRENT LIABILITIES	469	382
LONG-TERM DEBT	3	4
RETIREMENT BENEFITS	23	23
INTERCOMPANY PAYABLE (RECEIVABLE)	98	172
OTHER LIABILITIES	103	68
EQUITY ATTRIBUTABLE TO MERITOR, INC.	689	712
NONCONTROLLING INTERESTS	32	30
TOTAL LIABILITIES AND EQUITY	$ 1,417	$ 1,391