LONG-TERM DEBT - Capital Leases (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Capital Leased Assets [Line Items]
Capital lease term	60 months
Future Minimum Payments Due by Fiscal Year Maturity
Capital lease obligation, total	$ 15
Capital lease obligation, 2018	5
Capital lease obligation, 2019	3
Capital lease obligation, 2020	2
Capital lease obligation, 2021	2
Capital lease obligation, 2022	2
Capital lease obligation, Thereafter	1
Less amounts representing interest, total	(3)
Amounts representing interest, 2018	(1)
Amounts representing interest, 2019	(1)
Amounts representing interest, 2020	(1)
Amounts representing interest, 2021	0
Amounts representing interest, 2022	0
Amounts representing interest, Thereafter	0
Principal on capital lease, total	12
Principal on capital lease, 2018	4
Principal on capital lease, 2019	2
Principal on capital lease, 2020	1
Principal on capital lease, 2021	2
Principal on capital lease, 2022	2
Principal on capital lease, Thereafter	1
Capital Lease Arrangements
Capital Leased Assets [Line Items]
Amount outstanding under capital leases	$ 3	$ 7
Capital Lease Arrangements \| Five-Year Swap Rate
Capital Leased Assets [Line Items]
Basis spread on variable rate	5.64%
Other Capital Lease Arrangements
Capital Leased Assets [Line Items]
Amount outstanding under capital leases	$ 10	$ 9

Capital Leases, Future Minimum Payments, Interest Included In Payments, Due In Five Years

No definition available.

Name:	mtor_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInFiveYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Interest Included In Payments, Due In Four Years

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInFourYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Interest Included In Payments, Due In Three Years

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInThreeYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Interest Included In Payments, Due In Two Years

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInTwoYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Interest Included In Payments, Next Twelve Months

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsNextTwelveMonths
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Interest Included In Payments, Thereafter

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsThereafter
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Present Value Of Net Minimum Payments, Due In Five Years

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInFiveYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Present Value Of Net Minimum Payments, Due In Four Years

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInFourYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Present Value Of Net Minimum Payments, Due In Three Years

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInThreeYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Present Value Of Net Minimum Payments, Due In Two Years

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInTwoYears
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Present Value Of Net Minimum Payments, Due Next Twelve Months

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueNextTwelveMonths
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Capital Leases, Future Minimum Payments, Present Value Of Net Minimum Payments, Thereafter

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsThereafter
Namespace Prefix:	mtor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Capital lease term.

+ References

No definition available.

+ Details

Name:	mtor_CapitalLeasesTerm
Namespace Prefix:	mtor_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_CapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_CapitalLeasedAssetsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of minimum lease payments for capital leases.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDueAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of minimum lease payments for capital leases due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDueCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum lease payments for capital leases due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDueInFiveYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum lease payments for capital leases due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDueInFourYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum lease payments for capital leases due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDueInThreeYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum lease payments for capital leases due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDueInTwoYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum lease payments for capital leases due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsDueThereafter
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount necessary to reduce net minimum lease payments to present value for capital leases.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Present value of minimum lease payments for capital leases net of executory costs, including amounts paid by the lessee to the lessor for insurance, maintenance and taxes.

+ References

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	mtor_ArrangementsAxis=mtor_CapitalLeaseArrangementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=mtor_FiveYearSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mtor_ArrangementsAxis=mtor_OtherCapitalLeaseArrangementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: