Description of Business and Basis of Presentation	12 Months Ended
Description of Business and Basis of Presentation	Dec. 31, 2023
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation Description of Business Avidity Biosciences, Inc. (the Company or Avidity) is a biopharmaceutical company committed to delivering a new class of RNA therapeutics called Antibody Oligonucleotide Conjugates (AOCs). The Company’s proprietary AOC platform is designed to combine the specificity of monoclonal antibodies with the precision of RNA therapeutics to target the root cause of diseases previously untreatable with such therapeutics. Liquidity Since inception, the Company has relied on various means of raising capital, including public offerings, various sales agreements, the sale and issuance of convertible preferred stock, funding under collaboration agreements, and a private placement of common stock. The Company has devoted substantially all of its resources to organizing and staffing the Company, business planning, raising capital, developing its proprietary AOC platform, identifying potential product candidates, establishing its intellectual property portfolio, conducting research, preclinical studies, advancing its clinical programs and providing other general and administrative support for these operations. In addition, the Company has a limited operating history, has incurred operating losses since inception and expects that it will continue to incur net losses into the foreseeable future as it continues the development of its product candidates and development programs. As of December 31, 2023, the Company had an accumulated deficit of $570.8 million and cash, cash equivalents, and marketable securities of $595.4 million. The Company believes that existing cash, cash equivalents and marketable securities will be sufficient to fund the Company’s operations for at least 12 months from the date of the filing of this Form 10-K. The Company plans to finance its future cash needs through equity offerings, debt financings or other capital sources, including potential collaborations, licenses and other similar arrangements. If the Company is not able to secure adequate additional funding, it may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, and/or delay or reduce the scope of its planned development programs. Any of these actions could materially harm the Company’s business, results of operations, and future prospects. Basis of Presentation The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and the rules and regulations of the Securities and Exchange Commission (SEC). The financial statements reflect all adjustments which, in the opinion of management, are necessary for a fair presentation of the results for the periods presented. All such adjustments are of a normal and recurring nature. The operating results presented in these financial statements are not necessarily indicative of the results that may be expected for any future periods. In December 2023, the Company formed Avidity Biosciences Ireland Limited, a wholly-owned subsidiary (the Subsidiary). During 2023, there were no operations in the Subsidiary and there were no assets or liabilities held by the Subsidiary at December 31, 2023. Immaterial Out of Period Adjustment During the year ended December 31, 2023, the Company identified an immaterial adjustment to research and development expenses that impacted the Company’s previously issued financial statements. Therefore, the Company recorded an out of period adjustment that decreased research and development expenses for the year ended December 31, 2023 by $3.6 million, which related to the year ended December 31, 2022.