Leases - Leases in Condensed Consolidated Balance Sheet (Details) $ in Millions	Mar. 31, 2020 USD ($)
Finance Lease Assets And Liabilities Lessee
Finance lease right-of-use assets, Net Property	$ 6
Finance lease right-of-use assets, Balance Sheet [Extensible List]	mtor:PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetafterAccumulatedDepreciationandAmortization
Finance lease liabilities, Short-term debt	$ 2
Finance lease liabilities, current, Balance Sheet [Extensible List]	us-gaap:LongTermDebtCurrent
Finance lease liabilities, Long-term debt	$ 4
Finance lease liabilities, noncurrent, Balance Sheet [Extensible List]	us-gaap:LongTermDebtNoncurrent
Operating Lease Assets And Liabilities Lessee
Operating lease right-of-use assets, Other assets	$ 77
Operating lease right-of-use assets, Balance Sheet [Extensible List]	us-gaap:OtherAssetsNoncurrent
Operating lease liabilities, Other current liabilities	$ 14
Operating lease liabilities, current, Balance Sheet [Extensible List]	us-gaap:OtherLiabilitiesCurrent
Operating lease liabilities, Other liabilities	$ 63
Operating lease liabilities, noncurrent, Balance Sheet [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent