SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Sep. 30, 2015
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America (GAAP) requires the use of estimates and assumptions related to the reporting of assets, liabilities, revenues, expenses and related disclosures. Actual results could differ from these estimates. Significant estimates and assumptions were used to review goodwill and other long-lived assets for impairment (see Notes 4 and 11), costs associated with the company’s restructuring actions (see Note 5), product warranty liabilities (see Note 14), long-term incentive compensation plan obligations (see Note 19), retiree medical and pension obligations (see Notes 20 and 21), income taxes (see Note 22), and contingencies including asbestos
Concentration of Credit Risk	Concentration of Credit Risk In the normal course of business, the company provides credit to customers. The company limits its credit risk by performing ongoing credit evaluations of its customers and maintaining reserves for potential credit losses and through accounts receivable factoring programs. The company’s accounts receivable is due from medium- and heavy-duty truck OEMs, specialty vehicle manufacturers, aftermarket customers, and trailer producers.
Consolidation and Joint Ventures	Consolidation and Joint Ventures The consolidated financial statements include the accounts of the company and those subsidiaries in which the company has control. All intercompany balances and transactions are eliminated in consolidation. The results of operations of controlled subsidiaries are included in the consolidated financial statements and are offset by a related noncontrolling interest recorded for the noncontrolling partners’ ownership. Investments in affiliates that are not controlled or majority-owned are reported using the equity method of accounting (see Note 13).
Foreign Currency	Foreign Currency Local currencies are generally considered the functional currencies for operations outside the U.S. For operations reporting in local currencies, assets and liabilities are translated at year-end exchange rates with cumulative currency translation adjustments included as a component of Accumulated Other Comprehensive Loss in the consolidated balance sheet. Income and expense items are translated at average rates of exchange during the year.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets, excluding goodwill, to be held and used are reviewed for impairment whenever adverse events or changes in circumstances indicate a possible impairment. An impairment loss is recognized when a long-lived asset’s carrying value exceeds the fair value. Long-lived assets held for sale are recorded at the lower of their carrying amount or estimated fair value less cost to sell.
Discontinued Operations	Discontinued Operations A business component that either has been disposed of or is classified as held for sale is reported as discontinued operations if the cash flows of the component have been or will be eliminated from the ongoing operations of the company, and the company will no longer have any significant continuing involvement in the business component. The results of discontinued operations are aggregated and presented separately in the consolidated statement of operations and consolidated statement of cash flows (see Note 3).
Revenue Recognition	Revenue Recognition Revenues are recognized upon shipment of product and transfer of ownership to the customer. Provisions for customer sales allowances and incentives are recorded as a reduction of sales at the time of product shipment.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts An allowance for uncollectible trade receivables is recorded when accounts are deemed uncollectible based on consideration of write-off history, aging analysis, and any specific, known troubled accounts.
Earnings per Share	Earnings per Share Basic earnings (loss) per share is calculated using the weighted average number of shares outstanding during each period. The diluted earnings (loss) per share calculation includes the impact of dilutive common stock options, restricted shares, performance share awards, and convertible securities, if applicable.
Other	Other Other significant accounting policies are included in the related notes, specifically, goodwill (Note 4), inventories (Note 9), property and depreciation (Note 11), capitalized software (Note 12), product warranties (Note 14), financial instruments (Note 17), equity based compensation (Note 19), retirement medical plans (Note 20), retirement pension plans (Note 21), income taxes (Note 22) and environmental and asbestos-related liabilities (Note 23).
Accounting Standards to be Implemented and Implemented in Fiscal Year 2014	Accounting standards to be implemented In April 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-08, Presentation of Financial Statements and Property, Plant, and Equipment: Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. This guidance changes the definition of a discontinued operation to include only those disposals of components of an entity that represent a strategic shift that has (or will have) a major effect on an entity’s operations and financial results. The guidance also requires new disclosure of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. This guidance is effective for fiscal periods beginning after December 15, 2014, and is to be applied prospectively. The company will adopt this guidance as of October 1, 2015. The company does not expect any material impact on its consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with customers, which requires companies to recognize revenue when a customer obtains control rather than when companies have transferred substantially all risks and rewards of a good or service and requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. ASU 2014-09 was originally effective for annual reporting periods beginning on or after December 15, 2016 and interim periods therein. In August 2015, the FASB issued a deferral of ASU 2014-09 of one year making it effective for annual reporting periods beginning on or after December 15, 2017 while also providing for early adoption but not before the original effective date. The company plans to implement this standard in the first quarter of the fiscal year beginning October 1, 2018 and is currently evaluating the potential impact of this new guidance on its consolidated financial statements. In June 2014, the FASB issued ASU 2014-12, Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could be Achieved After the Requisite Service Period. This guidance requires that an award with a performance target that affects vesting, and that could be achieved after the requisite service period, such as when an employee retires but may still vest if and when the performance target is achieved, be treated as an award with performance conditions that affect vesting and the company apply existing guidance under ASC Topic 718, Compensation - Stock Compensation. The guidance is effective for fiscal years beginning after December 15, 2015 and may be applied either prospectively or retrospectively. The company is assessing the potential impact of this new guidance on its consolidated financial statements. In August 2014, the FASB issued ASU 2014-15 Presentation of Financial Statements - Going Concern, which provide guidance about management's responsibility in evaluating whether there is substantial doubt relating to an entity’s ability to continue as a going concern and to provide related footnote disclosures as applicable. ASU 2014-15 is effective for the interim and annual periods ending after December 15, 2016. Early adoption is permitted. The company does not expect any material impact on its consolidated financial statements from adoption of this guidance. In July 2015, the FASB issued ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, which requires entities that measure inventory using first-in, first-out (FIFO) or average cost to measure inventory at the lower of cost and net realizable value. The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2016 and interim periods within those annual periods. The company is assessing the potential impact of this new guidance on its consolidated financial statements. In September 2015, the FASB issued ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments, which updates Business Combination (Topic 805) guidance to eliminate the requirement to restate prior period financial statements for measurement period adjustments. The guidance should be applied prospectively to measurement period adjustments that occur after the effective date. The guidance is effective for interim and annual periods beginning after December 15, 2015. Early adoption is permitted. The company plans to implement this standard in the first quarter of the fiscal year beginning October 1, 2015 and is currently evaluating the potential impact of this new guidance on its consolidated financial statements. Accounting standards implemented during fiscal year 2015 In April 2015, the FASB issued ASU 2015-03, Interest — Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs. In June 2015, the FASB amended ASU 2015-03 with ASU 2015-15. Together the standard updates change the presentation of debt issuance costs for term debt in the balance sheet by requiring the debt issuance costs be presented as a direct deduction from the related debt liability, rather than recorded as an asset. This guidance is effective for periods beginning after December 15, 2015, and interim periods within those annual periods applied retrospectively. Early adoption is permitted. The company adopted this guidance in the fourth quarter of fiscal year 2015. Debt issuance costs associated with term debt were $17 million as of September 30, 2015 and 2014. In April 2015, the FASB issued ASU 2015-04 (Topic 820): Practical Expedient for the Measurement Date of an Employer’s Defined Benefit Obligation and Plan Assets. Under the new guidance, if an employer’s fiscal year-end does not coincide with a month-end, the employer may measure plan assets and benefit obligations using the month-end that is closest to the employer’s fiscal year-end. Early adoption is permitted. This guidance must be applied prospectively. The company adopted this guidance in the fourth quarter of fiscal year 2015 and the adoption did not have a material impact on the company's consolidated statement of financial position, results of operations, or cash flows. In April 2015, the FASB issued ASU 2015-05, Intangibles — Goodwill and Other — Internal-Use Software. ASU 2015-05 requires a company to determine whether a cloud computing arrangement contains a software license. If the arrangement contains a software license, the customer would account for the fees related to the software license element in a manner consistent with the accounting for the acquisition of other software licenses under ASC 350-40; if the arrangement does not contain a software license, the customer would account for the arrangement as a service contract. The standard is required to be adopted by public business entities in annual periods beginning after December 15, 2015, and interim periods within those annual periods. Early adoption is permitted. The company adopted this guidance concurrent with an annual review of the company's accounting for internal-use computer software costs policy as of June 30, 2015. The guidance is applied prospectively. The adoption did not have a material impact on the company's consolidated statement of financial position, results of operations, or cash flows. As new contracts are entered into or existing contracts are materially modified, the adoption may impact fixed assets, selling, general and administrative costs, or cost of sales. In May 2015, the FASB issued ASU 2015-07, Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share (or its Equivalent). Under the new guidance, investments measured at net asset value, as a practical expedient for fair value, are excluded from the fair value hierarchy. The new guidance requires reporting entities to reconcile the fair value hierarchy disclosure to the balance sheet by disclosing the amount of investments measured using the practical expedient. The standard is required to be adopted in annual periods beginning after December 15, 2015 and interim periods within those annual periods. Early adoption is permitted. This guidance must be applied retrospectively to all periods presented. The company adopted this guidance in the fourth quarter of fiscal year 2015. In Note 21, pension assets of $710 million and $849 million are disclosed as investments measured using the practical expedient as September 30, 2015 and 2014, respectively.
Inventories	Inventories are stated at the lower of cost (using FIFO or average methods) or market (determined on the basis of estimated realizable values)
Net Property	Property is stated at cost. Depreciation of property is based on estimated useful lives, generally using the straight-line method. Estimated useful lives for buildings and improvements range from 10 to 50 years and estimated useful lives for machinery and equipment range from 3 to 20 years. Significant improvements are capitalized, and disposed or replaced property is written off. Maintenance and repairs are charged to expense in the period they are incurred. Company-owned tooling is classified as property and depreciated over the shorter of its expected life or the life of the production contract, generally not to exceed three years. In accordance with the FASB guidance on property, plant and equipment, the company reviews the carrying value of long-lived assets, excluding goodwill, to be held and used, for impairment whenever events or changes in circumstances indicate a possible impairment. An impairment loss is recognized when a long-lived asset’s carrying value is not recoverable and exceeds estimated fair value.
Internal Use Software	In accordance with FASB ASC Topic 350-40, costs relating to internally developed or purchased software in the preliminary project stage and the post-implementation stage are expensed as incurred. Costs in the application development stage that meet the criteria for capitalization are capitalized and amortized using the straight-line basis over the estimated economic useful life of the software.
Product Warranty	The company records estimated product warranty costs at the time of shipment of products to customers. Warranty reserves are primarily based on factors that include past claims experience, sales history, product manufacturing and engineering changes and industry developments. Liabilities for product recall campaigns are recorded at the time the company’s obligation is probable and can be reasonably estimated. Policy repair actions to maintain customer relationship are recorded as other liabilities at the time an obligation is probable and can be reasonably estimated. Product warranties, including recall campaigns, not expected to be paid within one year are recorded as a non-current liability.
Environmental Costs	Federal, state and local requirements relating to the discharge of substances into the environment, the disposal of hazardous wastes and other activities affecting the environment have, and will continue to have, an impact on the operations of the company. The process of estimating environmental liabilities is complex and dependent upon evolving physical and scientific data at the sites, uncertainties as to remedies and technologies to be used and the outcome of discussions with regulatory agencies. The company records liabilities for environmental issues in the accounting period in which they are considered to be probable and the cost can be reasonably estimated. At environmental sites in which more than one potentially responsible party has been identified, the company records a liability for its allocable share of costs related to its involvement with the site, as well as an allocable share of costs related to insolvent parties or unidentified shares. At environmental sites in which Meritor is the only potentially responsible party, the company records a liability for the total probable and estimable costs of remediation before consideration of recovery from insurers or other third parties.