Organization and Basis of Presentation	6 Months Ended
Organization and Basis of Presentation	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	1. ORGANIZATION AND BASIS OF PRESENTATION Organization We are a global Tier 1 supplier to the automotive industry. We design, engineer and manufacture driveline, metal forming and casting products that are making the next generation of vehicles smarter, lighter, safer and more efficient. We employ over 25,000 associates, operating at nearly 90 facilities in 17 countries, to support our customers on global and regional platforms with a focus on quality, operational excellence and technology leadership. In the first quarter of 2019, we initiated a new global restructuring program (the 2019 Program) to further streamline our business by consolidating our four existing segments into three segments. This activity occurred through the disaggregation of our Powertrain segment, with a portion moving into our Driveline segment and a portion moving into our Metal Forming segment. See Note 3 - Restructuring and Acquisition-Related Costs for more detail on this reorganization. Basis of Presentation We have prepared the accompanying interim condensed consolidated financial statements in accordance with the instructions to Form 10-Q under the Securities Exchange Act of 1934. These condensed consolidated financial statements are unaudited but include all normal recurring adjustments, which we consider necessary for a fair presentation of the information set forth herein. Results of operations for the periods presented are not necessarily indicative of the results for the full fiscal year. The balance sheet at December 31, 2018 presented herein has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States of America (GAAP) for complete consolidated financial statements. In order to prepare the accompanying interim condensed consolidated financial statements, we are required to make estimates and assumptions that affect the reported amounts and disclosures in our interim condensed consolidated financial statements. Actual results could differ from those estimates. For further information, refer to the audited consolidated financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2018. Effect of New Accounting Standards Accounting Standard 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 may be applied either retrospectively or prospectively. We expect to adopt this guidance prospectively on January 1, 2020 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. This guidance became effective on January 1, 2019, and we elected to reclassify the stranded tax effects caused by the 2017 Tax Cuts and Jobs Act, resulting in a decrease in Accumulated other comprehensive income (loss) and an increase in Retained earnings of $27.7 million at January 1, 2019. 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 is 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 previous 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 are not significantly changed from previous lease guidance. This guidance became effective for AAM on January 1, 2019. See Note 2 - Leasing for additional detail regarding the adoption of ASU 2016-02.