Description of Business	9 Months Ended
Description of Business	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	DESCRIPTION OF BUSINESS AMAG Pharmaceuticals, Inc., a Delaware corporation, was founded in 1981. Throughout this Quarterly Report on Form 10-Q, AMAG Pharmaceuticals, Inc. and our consolidated subsidiaries are collectively referred to as “the Company,” “AMAG,” “we,” “us,” or “our.” We are a pharmaceutical company focused on bringing innovative products to patients with unmet medical needs by leveraging our development and commercial expertise to invest in and grow our pharmaceutical products and product candidates across a range of therapeutic areas. As of September 30, 2020, we marketed products that support the health of patients in the areas of hematology and maternal health, including Feraheme® (ferumoxytol injection) for intravenous use and Makena® (hydroxyprogesterone caproate injection) auto-injector. In addition to our approved products, our portfolio includes ciraparantag, a product candidate that is being studied as an anticoagulant reversal agent. In December 2019, we completed a review of our product portfolio and strategy. This strategic review resulted in our intention to divest our women’s health assets, as announced in January 2020, and as previously disclosed, we completed the divestiture of Intrarosa® (prasterone) during the second quarter of 2020. We completed the divestiture of our remaining women’s health asset, Vyleesi® (bremelanotide injection), in July 2020, which we determined did not meet the criteria for presentation as a discontinued operation, as it did not represent a strategic shift to our business as described above. For additional details on our divestiture of Vyleesi, refer to Note O, “Acquisitions, Collaboration, License and other Strategic Agreements”. In July 2020, we also decided to stop the AMAG-423 Phase 2b/3a study based, primarily, on the results of an interim analysis conducted by the study’s independent Data Safety Monitoring Board (“DSMB”). For additional details on our decision to stop the AMAG 423 study, refer to Note O, “Acquisitions, Collaboration, License and other Strategic Agreements”. On October 1, 2020, we entered into an Agreement and Plan of Merger with Covis Group S.à r.l., a Luxembourg company (“Covis”), Covis Mergerco Inc., a Delaware corporation and an indirect wholly owned subsidiary of Covis (“Merger Sub”), and (in respect of specific matters) Covis Finco S.à r.l., a Luxembourg company (the “Merger Agreement”), pursuant to which Merger Sub launched a cash tender offer (the “Offer”) to acquire all of the issued and outstanding shares of common stock of AMAG at a price per share of $13.75, net to the seller in cash, without interest. The Offer commenced on October 15, 2020 and will remain open for a minimum of 20 business days. The completion of the Offer is subject to customary closing conditions. For additional information, see Note T, “Subsequent Events”. On October 5, 2020, we received notice of the FDA’s Center for Drug Evaluation and Research proposal to withdraw marketing approval of Makena and notice of our opportunity to request a hearing. For additional information, refer to Note T, “Subsequent Events”. COVID-19 The global spread of COVID-19 has created significant volatility, uncertainty and economic disruption on a global scale, including in the United States, where we market our products, where our operations and employees reside and where we conduct clinical trials. The COVID-19 pandemic did not significantly impact our financial results during the three months ended September 30, 2020. The extent to which the COVID-19 pandemic impacts our business, operations and financial results in the future will depend on numerous evolving factors that we may not be able to accurately predict. While there have been no material impairments to date, any prolonged material disruptions to our sales, supply, research and development efforts and/or operations could negatively impact the Company’s business, operations and/or financial results.