Organization and Description of Business	6 Months Ended
Organization and Description of Business	Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Description of Business PhaseBio Pharmaceuticals, Inc. (the “Company”) was incorporated as a Delaware corporation on January 10, 2002. The Company is a clinical-stage biopharmaceutical company focused on the development and commercialization of novel therapies for cardiovascular diseases. The Company’s lead product candidate, bentracimab (also known as PB2452), is a novel reversal agent for the antiplatelet drug ticagrelor. The Company is also developing its preclinical product candidate, PB6440, for treatment-resistant hypertension. Going Concern The Company has experienced net losses and negative cash flows from operations and, as of June 30, 2022, had an accumulated deficit of $419.6 million. The Company expects to continue to incur net losses for at least the next several years. As of June 30, 2022, the Company had cash and cash equivalents of $7.8 million and negative working capital of $13.1 million. In January 2020, the Company entered into a co-development agreement (the "SFJ Agreement") with SFJ Pharmaceuticals X, Ltd., an SFJ Pharmaceuticals Group company ("SFJ"), pursuant to which SFJ provides funding and operational support for the clinical development of bentracimab. Management believes that its existing cash and cash equivalents as of June 30, 2022, in addition to the $21.0 million in clinical trial costs and other expenses that the Company expects SFJ will fund or reimburse pursuant to the SFJ Agreement, will not be sufficient to fund operating expenses and capital requirements for 12 months from the date of the issuance of these condensed financial statements. These factors raise substantial doubt about the Company's ability to continue as a going concern. The condensed financial statements do not include any adjustments that might result from the outcome of this uncertainty. Under the SFJ Agreement, if the Company fails to remedy such going concern condition during the periods specified in the agreement, SFJ may elect to have the Company's business related to bentracimab transferred to SFJ. The Company plans to address its liquidity needs through the pursuit of additional funding through a combination of equity or debt financings, or other third-party financing, marketing and distribution arrangements and other collaborations, strategic alliances and transactions and licensing arrangements. However, there is no assurance that these funding efforts will be successful. In this regard, the Company currently has an effective shelf registration statement on Form S-3 (the "2019 Shelf Registration Statement") on file with the Securities and Exchange Commission ("SEC"), which expires in January 2023. The 2019 Shelf Registration Statement currently permits (i) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $200.0 million of common stock, preferred stock, debt securities and warrants in one or more offerings and in any combination and (ii) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $60.0 million of common stock that may be issued and sold under an "at-the-market" sales agreement (the "ATM Program"). The $60.0 million of common stock that may be issued and sold under the ATM Program is included in the $200.0 million of securities that may be issued and sold under the 2019 Shelf Registration Statement. As of June 30, 2022, the Company had $130.6 million of common stock remaining that can be sold under the 2019 Shelf Registration Statement, of which $55.0 million may be sold under the ATM Program. The Company is continuing to assess the effect that the COVID-19 pandemic, geopolitical tensions, such as Russia's incursion into Ukraine, and the resulting global slowdown of economic activity, decades-high inflation, rising interest rates, and a potential recession in the United States may have on its business and operations. The extent to which these uncertainties may impact the Company's business and operations will depend on future developments that are highly uncertain and cannot be predicted with confidence, such as the duration and effect of business disruptions, the geographic distribution of COVID-19 and its variants over time, the efficacy and availability and pace of administration of vaccines and antiviral agents against the disease, the continued duration of the outbreak, and the short-term effects and ultimate effectiveness of the travel restrictions, quarantines, social distancing requirements and business closures in the United States and other countries to contain and treat the disease. While the potential economic impact brought by, and the continued duration of, these uncertainties may be difficult to assess or predict, continued adverse macroeconomic conditions and the growing pandemic have resulted in and could result in further significant disruption of global financial markets, reducing the Company's ability to access capital, which could in the future negatively affect its liquidity. In addition, a recession or market correction resulting from the spread of COVID-19, geopolitical tensions or other macroeconomic factors could materially affect the Company's business and the value of its common stock. Basis of Presentation The accompanying condensed financial statements have been prepared in accordance with United States generally accepted accounting principles (“GAAP”) for interim financial reporting and the rules and regulations of the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. All adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the accompanying condensed financial statements have been made. Although these interim financial statements do not include all of the information and footnotes required for complete annual financial statements, management believes the disclosures are adequate to make the information presented not misleading. The unaudited interim results of operations and cash flows for the three and six months ended June 30, 2022 are not necessarily indicative of the results that may be expected for the full year. The unaudited interim condensed financial statements and footnotes should be read in conjunction with the audited financial statements and footnotes for the year ended December 31, 2021, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 24, 2022, wherein a more complete discussion of significant accounting policies and certain other information can be found. Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board (“FASB”). The Company manages its operations as a single reportable segment for the purposes of assessing performance and making operating decisions.