Organization and Basis of Presentation (Policies)	12 Months Ended
Organization and Basis of Presentation (Policies)	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation, Policy [Policy Text Block]	PRINCIPLES OF CONSOLIDATION We include the accounts of Holdings and its subsidiaries in our consolidated financial statements. We eliminate the effects of all intercompany transactions, balances and profits in our consolidation.
Revenue Recognition, Policy [Policy Text Block]	REVENUE RECOGNITION We are obligated under our contracts with customers to manufacture and supply products for use in our customers’ operations. We satisfy these performance obligations at the point in time that the customer obtains control of the products, which is the point in time that the customer is able to direct the use of, and obtain substantially all of the remaining benefits from, the products. This typically occurs upon shipment to the customer in accordance with purchase orders and delivery releases issued by our customers. There is judgment involved in determining when the customer obtains control of the products and we have utilized the following indicators of control in our assessment: •We have the present right to payment for the asset; •The customer has legal title to the asset; •We have transferred physical possession of the asset; •The customer has the significant risks and rewards of ownership of the asset; and •The customer has accepted the asset. See Note 2 - Revenue from Contracts with Customers for more detail on our revenue.
Research and Development Expense, Policy [Policy Text Block]	RESEARCH AND DEVELOPMENT (R&D) COSTS We expense R&D, as incurred, in selling, general and administrative expenses on our Consolidated Statements of Operations. R&D spending was $146.2 million, $161.5 million and $139.8 million in 2018, 2017 and 2016, respectively.
Cash and Cash Equivalents, Policy [Policy Text Block]	CASH AND CASH EQUIVALENTS Cash and cash equivalents include all cash balances, savings accounts, sweep accounts, and highly liquid investments in money market funds and certificates of deposit with maturities of 90 days or less at the time of purchase.
Trade and Other Accounts Receivable, Policy [Policy Text Block]	ACCOUNTS RECEIVABLE The majority of our accounts receivable are due from original equipment manufacturers (OEMs) in the automotive industry and are past due when payment is not received within the terms stated within the contract. Trade accounts receivable for our customers are generally due within approximately 50 days from the date our customers receive our product. Amounts due from customers are stated net of allowances for doubtful accounts. We determine our allowances by considering factors such as the length of time accounts are past due, our previous loss history, the customer's ability to pay its obligation to us, and the condition of the general economy and the industry as a whole. The allowance for doubtful accounts was $8.4 million and $7.0 million as of December 31, 2018 and 2017, respectively. We write-off accounts receivable when they become uncollectible.
Property, Plant and Equipment, Preproduction Design and Development Costs [Policy Text Block]	CUSTOMER TOOLING AND PRE-PRODUCTION COSTS RELATED TO LONG-TERM SUPPLY AGREEMENTS Engineering, R&D, and other pre-production design and development costs for products sold on long-term supply arrangements are expensed as incurred unless we have a contractual guarantee for reimbursement from the customer. Reimbursements received for pre-production costs relating to awarded programs are deferred and recognized into revenue over the life of the associated program. Reimbursements received for pre-production costs relating to future programs that have not been awarded, or amounts received for programs that become discontinued prior to production, are recorded as a reduction of expense. Costs for tooling used to make products sold on long-term supply arrangements for which we have either title to the assets or the noncancelable right to use the assets during the term of the supply arrangement are capitalized in property, plant and equipment. Reimbursable costs for tooling assets for which our customer has title and we do not have a noncancelable right to use during the term of the supply arrangement, are recorded in accounts receivable in our consolidated balance sheets. The reimbursement for the customer-owned tooling is recorded as a reduction of accounts receivable upon collection. Capitalized items and customer receipts in excess of tooling costs specifically related to a supply arrangement are amortized over the shorter of the term of the arrangement or over the estimated useful lives of the related assets.
Inventory, Policy [Policy Text Block]	INVENTORIES We state our inventories at the lower of cost or net realizable value. The cost of our inventories is determined using the FIFO method. When we determine that our gross inventories exceed usage requirements, or if inventories become obsolete or otherwise not saleable, we record a provision for such loss as a component of our inventory accounts.
Property, Plant and Equipment, Policy [Policy Text Block]	PROPERTY, PLANT AND EQUIPMENT We state property, plant and equipment, including amortizable tooling, at historical cost, as adjusted for impairments. Construction in progress includes costs incurred for the construction of buildings and building improvements, and machinery and equipment in process. Repair and maintenance costs that do not extend the useful life or otherwise improve the utility of the asset beyond its existing useful state are expensed in the period incurred. We record depreciation and tooling amortization using the straight-line method over the estimated useful lives of the depreciable assets. Depreciation and tooling amortization amounted to $367.0 million, $301.6 million and $160.4 million in 2018, 2017 and 2016, respectively.
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	IMPAIRMENT OF LONG-LIVED ASSETS When impairment indicators exist, we evaluate the carrying value of long-lived assets for potential impairment. We consider projected future undiscounted cash flows, trends and other circumstances in making such estimates and evaluations. If impairment is deemed to exist, the carrying amount of the asset is adjusted based on its fair value. Recoverability of assets “held for use” is determined by comparing the forecasted undiscounted cash flows of the operations to which the assets relate to their carrying amount. When the carrying value of an asset group exceeds its fair value and is therefore nonrecoverable, those assets are written down to fair value. Fair value is determined based on market prices, when available, or a discounted cash flow analysis is performed using management estimates.
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	GOODWILL We record goodwill when the purchase price of acquired businesses exceeds the value of their identifiable net tangible and intangible assets acquired. We test our goodwill annually as of October 1, or more frequently if necessary, for impairment in accordance with the accounting guidance for goodwill and other indefinite-lived intangibles. See Note 5 - Goodwill and Other Intangible Assets, for more detail on our goodwill.
Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block]	OTHER INTANGIBLE ASSETS In connection with our acquisitions of USM Mexico Manufacturing LLC (USM Mexico) and MPG, we recognized $1,254.8 million of amortizable intangible assets for customer platforms, customer relationships, developed technology and licensing agreements. These intangible assets were assigned useful lives ranging from five to 17 years from the dates of the acquisitions. The intangible assets were valued using primarily the relief from royalty method or the multi-period excess earnings method, both of which utilize significant unobservable inputs. These inputs are defined in the fair value hierarchy as Level 3 inputs, which require management to make estimates and assumptions regarding certain financial measures using forecasted or projected information. See Note 5 - Goodwill and Other Intangible Assets, for more detail on our intangible assets.
Debt, Policy [Policy Text Block]	DEBT ISSUANCE COSTS The costs related to the issuance or modification of long-term debt are deferred and amortized into interest expense over the expected life of the borrowings. As of December 31, 2018 and December 31, 2017, our unamortized debt issuance costs were $80.7 million and $93.1 million, respectively. Debt issuance costs associated with our senior unsecured notes, as well as our Term Loan A Facility and Term Loan B Facility (as defined in Note 6 - Long-Term Debt and Lease Obligations), are recorded as a reduction to the related debt liability. Debt issuance costs of $13.6 million and $17.5 million related to our Revolving Credit Facility (also as defined in Note 6 - Long-Term Debt and Lease Obligations), are classified as Other assets and deferred charges on our Consolidated Balance Sheets as of December 31, 2018 and December 31, 2017, respectively. Unamortized debt issuance costs that exist upon the extinguishment of debt are expensed and classified as Debt refinancing and redemption costs on our Consolidated Statements of Operations.
Derivatives, Policy [Policy Text Block]	DERIVATIVES We recognize all derivatives on the balance sheet at fair value and we are not subject to master netting agreements. If a derivative qualifies under the accounting guidance as a hedge, depending on the nature of the hedge, changes in the fair value of the derivative are either offset against the change in fair value of the hedged asset, liability or firm commitment through earnings or recognized in other comprehensive income until the hedged item is recognized in earnings. Changes in the fair value of derivatives that do not qualify as hedges, are immediately recognized in earnings. See Note 7 - Derivatives and Risk Management, for more detail on our derivatives.
Foreign Currency Transactions and Translations Policy [Policy Text Block]	CURRENCY TRANSLATION AND REMEASUREMENT We translate the assets and liabilities of our foreign subsidiaries to U.S. dollars at end-of-period exchange rates. We translate the income statement elements of our foreign subsidiaries to U.S. dollars at average-period exchange rates. We report the effect of translation for our foreign subsidiaries that use the local currency as their functional currency as a separate component of stockholders' equity. Gains and losses resulting from the remeasurement of assets and liabilities in a currency other than the functional currency of a subsidiary are reported in current period income. We also report any gains and losses arising from transactions denominated in a currency other than the functional currency of a subsidiary in current period income. These foreign currency gains and losses resulted in net losses of $0.2 million and $7.3 million for the years 2018 and 2017, respectively, and a net gain of $5.8 million for 2016, in Other income (expense).
Postemployment Benefit Plans, Policy [Policy Text Block]	PENSION AND OTHER POSTRETIREMENT DEFINED BENEFIT PLANS Net pension and postretirement benefit expenses and the related liabilities are determined on an actuarial basis. These plan expenses and obligations are dependent on management's assumptions developed in consultation with our actuaries. We review these actuarial assumptions at least annually and make modifications when appropriate. See Note 9 - Employee Benefit Plans, for more detail on our pension and other postretirement defined benefit plans.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	STOCK-BASED COMPENSATION We have stock-based compensation in the form of restricted stock units (RSUs) and performance shares. For non-performance based awards, the grant date fair value is measured as the stock price at the date of grant. For performance based awards, fair value is estimated using valuation techniques that require management to use estimates and assumptions. Certain awards require that management's estimates and assumptions be evaluated at each reporting date to determine if compensation expense related to the award should be adjusted, both on a catch-up and go-forward basis. Compensation expense is recognized over the period during which the requisite service is provided, referred to as the vesting period. See Note 10 - Stock-Based Compensation, for more detail on our accounting for stock-based compensation.
Income Tax, Policy [Policy Text Block]	DEFERRED INCOME TAX ASSETS AND LIABILITIES AND VALUATION ALLOWANCES Our deferred income tax assets and liabilities reflect the impact of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the basis of such assets and liabilities as measured by tax laws. In accordance with the accounting guidance for income taxes, we review the likelihood that we will realize the benefit of deferred tax assets and estimate whether recoverability of our deferred tax assets is “more likely than not,” based on forecasts of taxable income in the related tax jurisdictions. In determining the requirement for a valuation allowance, the historical results, projected future operating results based upon approved business plans, eligible carry forward periods, and tax planning opportunities are considered, along with other relevant positive and negative evidence. If, based upon available evidence, it is more likely than not the deferred tax assets will not be realized, a valuation allowance is recorded. We record uncertain tax positions on the basis of a two-step process whereby: (1) we determine whether it is "more likely than not" that the tax positions will be sustained based on the technical merits of the position: and (2) for those positions that meet the "more likely than not" recognition threshold, we recognize the largest amount of tax benefit that is greater than 50% likely to be realized upon ultimate settlement with the related tax authority. We record interest and penalties on uncertain tax positions in income tax expense (benefit). See Note 11 - Income Taxes, for more detail on our accounting for income taxes.
Earnings Per Share, Policy [Policy Text Block]	EARNINGS (LOSS) PER SHARE (EPS) We present EPS using the two-class method. This method allocates undistributed earnings between common shares and non-vested share based payment awards that entitle the holder to non-forfeitable dividend rights. Our participating securities include non-vested restricted stock units. See Note 12 - Earnings (Loss) Per Share (EPS), for more detail on our accounting for EPS.
Authorized Share Repurchase Program [Policy Text Block]	SHARE REPURCHASE PROGRAM In 2016, AAM's Board of Directors authorized a share repurchase program of up to $100 million of AAM's common shares as part of AAM's overall capital allocation strategy. The program expired on December 31, 2018. We repurchased a total of $1.5 million of shares under the share repurchase program and there were no share repurchases under the program during 2018.
Standard Product Warranty, Policy [Policy Text Block]	PRODUCT WARRANTY See Note 13 - Commitments and Contingencies, for detail on our accounting for product warranties.
Use of Estimates, Policy [Policy Text Block]	USE OF ESTIMATES In order to prepare consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP), we are required to make estimates and assumptions that affect the reported amounts and disclosures in our consolidated financial statements. Actual results could differ from those estimates.
New Accounting Pronouncements, Policy [Policy Text Block]	EFFECT OF NEW ACCOUNTING STANDARDS Accounting Standards Update 2018-15 On August 15, 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2018-15 - Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract (Topic 350-40). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a cloud computing or hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. This guidance becomes effective at the beginning of our 2020 fiscal year, and early adoption is permitted for financial statements which have not yet been issued. This guidance may be applied either retrospectively or prospectively and we are currently assessing the impact that this standard will have on our consolidated financial statements. Accounting Standards Update 2018-02 On February 14, 2018, the FASB issued ASU 2018-02 - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (Topic 220). ASU 2018-02 allows companies the option to reclassify disproportionate tax effects in accumulated other comprehensive income (AOCI) caused by the 2017 Tax Cuts and Jobs Act, also known as stranded tax effects, to retained earnings. ASU 2018-02 also requires expanded disclosures related to disproportionate income tax effects from AOCI, some of which are applicable to all companies regardless of whether the option to reclassify the stranded tax effects is exercised. The guidance becomes effective at the beginning of our 2019 fiscal year, and we expect to record an adjustment to AOCI and Retained earnings of approximately $28 million associated with the adoption of this guidance. Accounting Standards Update 2017-12 On August 28, 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2017-12 - Targeted Improvements to Accounting for Hedging Activities (Topic 815). ASU 2017-12 is intended to better align the risk management activities of a company with the company's financial reporting for hedging relationships. This guidance expands and refines several aspects of hedge accounting. The most applicable changes to AAM as a result of the new guidance are as follows: 1) the concept of risk component hedging is introduced in ASU 2017-12, which could allow us to hedge contractually specified components in a contract; 2) the guidance now allows entities to utilize a 31-day period in assessing whether the critical terms of a forecasted transaction match the maturity of the hedging derivative, which could allow for expanded use of hedging instruments for certain sales and purchases; and 3) we may now qualitatively assess hedge effectiveness on a quarterly basis when the facts and circumstances related to the hedging relationship have not changed significantly. This guidance becomes effective at the beginning of our 2019 fiscal year, however early adoption is permitted, and we have adopted this guidance effective January 1, 2018. The adoption of this guidance did not have any impact on the measurement or presentation of our existing hedging relationships. See Note 7 - Derivatives and Risk Management for additional detail on our hedging instruments. Accounting Standards Update 2017-07 On March 10, 2017, the FASB issued ASU 2017-07 - Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. The amendments in this update require that an employer disaggregate the service cost component from the other components of defined benefit pension cost and postretirement benefit cost (net benefit cost). Subsequent to the adoption of this guidance, only the service cost component of net benefit cost is included in the subtotal Operating income in our Consolidated Statements of Operations and only the service cost component is eligible for capitalization. This guidance became effective at the beginning of our 2018 fiscal year and required a retrospective transition method for the income statement classification of the net benefit cost components and a prospective transition method for the capitalization of the service cost component in assets. The adoption of this guidance did not have a material impact on our consolidated financial statements. Accounting Standards Update 2017-04 On January 26, 2017, the FASB issued ASU 2017-04 - Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. The amendments in this update modify the concept of impairment from the condition that exists when the carrying amount of goodwill exceeds its implied fair value to the condition that exists when the carrying amount of a reporting unit exceeds its fair value. An entity no longer will determine goodwill impairment by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination, or what is referred to under existing guidance as "Step 2." Instead, under the amendments in this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, an entity should consider income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable. This guidance becomes effective at the beginning of our 2020 fiscal year, however early adoption is permitted and we elected to early adopt this guidance in conjunction with our annual goodwill impairment test that was conducted in the fourth quarter of 2018. See Note 5 - Goodwill and Other Intangible Assets for further discussion regarding the results of our annual goodwill impairment test for 2018. Accounting Standards Update 2016-16 On October 24, 2016, the FASB issued Accounting Standards Update (ASU) 2016-16 - Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. Existing income tax guidance prohibits the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party. This existing guidance is deemed an exception to the principle of comprehensive recognition of current and deferred income taxes under accounting principles generally accepted in the United States of America (GAAP). Due to the limited authoritative guidance about this exception, diversity in practice exists. ASU 2016-16 eliminates this exception for intra-entity transfers of assets other than inventory and requires that entities recognize the income tax consequences when the transfers occur. This guidance was effective January 1, 2018 and required a modified retrospective transition method. The adoption of this guidance did not have a significant impact on our consolidated financial statements. Accounting Standards Update 2016-02 On February 25, 2016, the FASB issued ASU 2016-02 - Leases (Topic 842), and has subsequently issued ASU 2017-13 - Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840) and Leases (Topic 842) (collectively the Lease ASUs) which supersede the existing lease accounting guidance and establish new criteria for recognizing lease assets and liabilities. The most significant impact of these updates, to AAM, is that a lessee will be required to recognize a "right-of-use" asset and lease liability for operating lease agreements that were not previously included on the balance sheet under the existing lease guidance. Expense recognition in the statement of income along with cash flow statement classification for both financing (capital) and operating leases under the new standard will not be significantly changed from existing lease guidance. This guidance becomes effective for AAM at the beginning of our 2019 fiscal year. We are finalizing the inputs to our calculations and expect to record right-of-use assets and lease liabilities in the range of $85 million to $95 million as a result of implementing this guidance. We plan to elect the package of practical expedients that will allow us to 1) not reassess whether existing or expired contracts contain or contained a lease; 2) not reassess the classification (operating or financing) of our existing leases; and 3) not reassess initial direct costs for existing leases. We also plan to elect the optional transition method that will allow us to not retrospectively revise prior period balance sheets to include operating leases. We plan to also elect the practical expedient that will allow us to exclude recognition of a right-of-use asset and associated liability for lease terms of 12 months or less. Finally, we plan to elect the practical expedient to not separate lease and non-lease components in contracts that contain both, and will account for these types of contracts entirely as a single lease component. Accounting Standards Update 2014-09 In 2014, the FASB issued ASU 2014-09 - Revenue from Contracts with Customers (Topic 606), and has subsequently issued ASUs 2015-14 - Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, 2016-08 - Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross Versus Net), 2016-10 - Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, 2016-12 - Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, 2016-20 - Revenue from Contracts with Customers (Topic 606): Technical Corrections and Improvements to Topic 606 and 2017-13 - Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840) and Leases (Topic 842) (collectively, the Revenue Recognition ASUs). The Revenue Recognition ASUs outline a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersede most current revenue recognition guidance, including industry-specific guidance. The guidance is based on the principle that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to fulfill a contract. This guidance became effective for AAM on January 1, 2018 and we have adopted this guidance using the modified retrospective approach. See Note 2 - Revenue from Contracts with Customers for more detail.