Summary of significant accounting policies (Policies)	6 Months Ended
Summary of significant accounting policies (Policies)	Sep. 30, 2022
Accounting Policies [Abstract]
Principles of consolidation	The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") and include the accounts of the Company and its direct and indirect wholly owned subsidiaries, Replimune UK, Replimune US, Replimune Securities Corporation and Replimune (Ireland) Limited after elimination of all intercompany accounts and transactions.
Use of estimates	The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company's business, results of operations and financial condition, including, expenses, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19. The Company has made estimates of the impact of COVID-19 within the Company's financial statements and there may be changes to those estimates in future periods. On an ongoing basis, management evaluates its estimates in light of reasonable changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates or assumptions.
Unaudited interim financial information	The accompanying consolidated balance sheet as of September 30, 2022, the consolidated statements of operations, of comprehensive loss and of stockholders’ equity for the three and six months ended September 30, 2022 and 2021 and the consolidated statements of cash flows for the six months ended September 30, 2022 and 2021 are unaudited. The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2022 and the results of its operations for the three and six months ended September 30, 2022 and 2021 and its cash flows for the six months ended September 30, 2022 and 2021. The financial data and other information disclosed in these consolidated notes related to the three and six months ended September 30, 2022 and 2021 are unaudited. The results for the three and six months ended September 30, 2022 are not necessarily indicative of results to be expected for the year ending March 31, 2023, any other interim periods or any future year or period. The financial information included herein should be read in conjunction with the financial statements and notes in the Company's Annual Report on Form 10-K for the year ended March 31, 2022, which was filed with the Securities and Exchange Commission on May 19, 2022 (the "Annual Report"). During the three and six months ended September 30, 2022, there have been no changes to the Company’s significant accounting policies as described in the Annual Report, except as described below.
Recently adopted accounting pronouncements and Recently issued accounting pronouncements	Recently adopted accounting pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments- Credit Losses (Topic 326). The standard changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. Financial assets measured at amortized cost will be presented at the net amount expected to be collected by using an allowance for credit losses. The Company adopted ASU 2016-13 as of April 1, 2022. The adoption of ASU 2016-13 did not have a material impact on the Company's consolidated financial statements.