Description of the Business	9 Months Ended
Description of the Business	Sep. 30, 2022
Accounting Policies [Abstract]
Description of the Business	Description of the Business Gossamer Bio, Inc. (including its subsidiaries, referred to as “we,” “us,” “our,”, or the “Company”) is a clinical-stage biopharmaceutical company focused on discovering, acquiring, developing and commercializing therapeutics in the disease areas of immunology, inflammation and oncology. The Company was incorporated in the state of Delaware on October 25, 2015 (originally as FSG Bio, Inc.) and is based in San Diego, California. The unaudited condensed consolidated financial statements include the accounts of Gossamer Bio, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions among the consolidated entity have been eliminated in consolidation. Liquidity and Capital Resources The Company has incurred significant operating losses since its inception. As of September 30, 2022, the Company had an accumulated deficit of $976.5 million. From the Company’s inception through September 30, 2022, the Company has funded its operations primarily through equity and debt financings. The Company raised $1,062.1 million from October 2017 through September 30, 2022 through the sale of Series A and B convertible preferred stock, issuance of convertible notes, its initial public offering ("IPO"), the Credit Facility and 2027 Notes (as defined in Note 5 below), and issuances of common stock in May 2020 and July 2022. See Note 5 for additional information regarding the Credit Facility and the 2027 Notes. The Company expects to continue to incur significant operating losses for the foreseeable future and may never become profitable. As a result, the Company will need to raise additional capital through equity offerings, debt financings or other capital sources, including potential collaborations, licenses and other similar arrangements. Management believes that it has sufficient working capital on hand to fund operations through at least the next 12 months from the date these condensed consolidated financial statements were available to be issued. There can be no assurance that the Company will be successful in acquiring additional funding, that the Company’s projections of its future working capital needs will prove accurate, or that any additional funding would be sufficient to continue operations in future years. COVID-19 The COVID-19 pandemic has caused significant business disruption around the globe. The extent of the impact of COVID-19 on the Company’s operational and financial performance will depend on certain developments, including the duration and spread of the pandemic worldwide and the impact on the Company’s clinical trials, employees and vendors. To the extent possible, and consistent with applicable guidance from federal, state and local authorities, the Company is conducting business as usual. The Company will continue to actively monitor the evolving situation related to COVID-19 and may take further actions that alter its operations, including those that may be required by federal, state or local authorities, or that the Company determines are in the best interests of its employees and other third parties with whom the Company does business. At this point, the degree to which COVID-19, including new variants of the virus that causes COVID-19, may continue to impact the Company’s financial condition or results of operations remains uncertain. A prolonged pandemic could have a material and adverse impact on the financial results and business operations of the Company, including the timing and ability of the Company to complete certain clinical trials and other efforts required to advance the development of its product candidates and raise additional capital. For example, certain sites temporarily closed enrollment in the Company's Phase 2 clinical trial in pulmonary arterial hypertension ("PAH") in 2020 as a result of the COVID-19 pandemic and related staffing shortages at sites and key vendors. In addition, due to the challenges of enrolling patients worldwide posed by the COVID-19 pandemic and related staffing shortages at sites and key vendors, the Company previously experienced delays in enrollment of patients in its Phase 2 clinical trial of seralutinib, also known as GB002, in PAH.