Nature of Operations	3 Months Ended
Nature of Operations	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations Description of the business MacroGenics, Inc. (the Company) is incorporated in the state of Delaware. The Company is a biopharmaceutical company focused on developing and commercializing innovative antibody-based therapeutics designed to modulate the human immune response for the treatment of cancer. In December 2020, the U.S. Food and Drug Administration (FDA) approved MARGENZA (margetuximab-cmkb) in combination with chemotherapy for the treatment of adult patients with metastatic HER2-positive breast cancer who have received two or more prior anti-HER2 regimens, at least one of which was for metastatic disease. The Company launched MARGENZA in collaboration with our commercialization partner, Eversana Life Science Services, LLC (Eversana), in March 2021. In addition, the Company has a pipeline of product candidates in human clinical testing that have been created primarily using its proprietary, antibody-based technology platforms. The Company believes its product candidates have the potential to have a meaningful effect on treating patients' unmet medical needs as monotherapy or, in some cases, in combination with other therapeutic agents. Liquidity The Company’s multiple product candidates currently under development will require significant additional research and development efforts that include extensive preclinical studies and clinical testing, and regulatory approval prior to commercial use. As a biotechnology company, the Company has primarily funded its operations with proceeds from the sale of its common stock in equity offerings, revenue from its multiple collaboration agreements, and contracts and grants from the National Institute of Allergy and Infectious Diseases (NIAID). Management regularly reviews the Company’s available liquidity relative to its operating budget and forecast to monitor the sufficiency of the Company’s working capital, and anticipates continuing to draw upon available sources of capital, including equity and debt instruments, to support its product development activities. Based on the Company’s most recent cash flow forecast, the Company believes its current cash, cash equivalents and marketable securities is sufficient to fund its operating plans for a minimum of twelve months from the date that this Quarterly Report was filed. The Company plans to meet its near-term operating requirements primarily through cash and marketable securities on hand, and a combination of product sales and current and future strategic collaborations and alliances and marketing, distribution or licensing arrangements. In the longer term, the Company plans to meet its operating requirements by generating revenue from product sales to the extent its other product candidates receive marketing approval and can be commercialized, or by potential future equity or debt issuances. There can be no assurances that new sources of capital will be available to the Company on commercially acceptable terms, if at all. Also, any future collaborations, strategic alliances and marketing, distribution or licensing arrangements may require the Company to give up some or all rights to a product or technology at less than its full potential value. If the Company is unable to enter into new arrangements or to perform under current or future agreements or obtain additional capital, the Company will assess its capital resources and may be required to delay, reduce the scope of, or eliminate one or more of its product research and development programs or clinical studies, and/or downsize its organization. Similar to the other risk factors pertinent to the Company's business, the COVID-19 pandemic might unfavorably impact the Company's ability to generate such additional funding. Given the uncertainty in the rapidly changing market and economic conditions related to the COVID-19 pandemic, the Company will continue to evaluate the nature and extent of the impact of the outbreak on its business and financial position. Basis of Presentation The accompanying unaudited interim consolidated financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information. The financial statements include all adjustments (consisting only of normal recurring adjustments) that the management of the Company believes are necessary for a fair presentation of the periods presented. These interim financial results are not necessarily indicative of results expected for the full fiscal year or for any subsequent interim period. The accompanying unaudited interim consolidated financial statements include the accounts of MacroGenics, Inc. and its wholly owned subsidiaries, MacroGenics UK Limited and MacroGenics Limited. All intercompany accounts and transactions have been eliminated in consolidation. These consolidated financial statements and related notes should be read in conjunction with the financial statements and notes thereto included in the Company's 2020 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 25, 2021.