Description of the business	12 Months Ended
Description of the business	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the business	Description of the business bluebird bio, Inc. (the “Company” or “bluebird”) was incorporated in Delaware on April 16, 1992, and is headquartered in Somerville, Massachusetts. The Company is a biotechnology company committed to researching, developing and commercializing potentially curative gene therapies for severe genetic diseases based on its proprietary lentiviral vector ("LVV") gene addition platform. Since its inception, the Company has devoted substantially all of its resources to its research and development efforts relating to its product candidates, and commercialization of its approved products, including activities to manufacture product candidates, conduct clinical studies of its product candidates, perform preclinical research to identify new product candidates, provide selling, general and administrative support for these operations and market and commercially manufacture and distribute its approved products. The Company’s programs in severe genetic diseases include ZYNTEGLO (betibeglogene autotemcel, also known as beti-cel) as a treatment for β-thalassemia; LYFGENIA (lovotibeglogene autotemcel, also known as lovo-cel) as a treatment for sickle cell disease ("SCD"); and SKYSONA (elivaldogene autotemcel, also known as eli-cel) as a treatment for cerebral adrenoleukodystrophy ("CALD"). On August 17, 2022, ZYNTEGLO was approved by the U.S. Food and Drug Administration (“FDA”) for the treatment of adult and pediatric patients with ß-thalassemia who require regular red blood cell transfusions. On September 16, 2022, the FDA granted Accelerated Approval of SKYSONA to slow the progression of neurologic dysfunction in boys 4-17 years of age with early, active CALD. On December 8, 2023, LYFGENIA was approved by the FDA for the treatment of patients 12 years of age or older with sickle cell disease and with a history of vaso-occlusive-events. In April 2022, the Board of Directors of the Company approved a comprehensive restructuring plan intended to reduce operating expenses and enhance the Company’s focus on achieving FDA approval for its programs in the U.S. As part of the restructuring, the Company reduced its workforce by approximately 30% across the second and third quarters of 2022. Refer to Note 19, Reduction in workforce, for more information on this restructuring. In June 2022, the Company entered into an Equity Distribution Agreement (the “Equity Distribution Agreement”) with Goldman Sachs & Co. LLC (“Goldman”) to sell shares of the Company’s common stock up to $75.0 million, from time to time, through an “at the market” equity offering program under which Goldman would act as manager. Under the Equity Distribution Agreement, the Company paid to Goldman a commission equal to up to 3.0% of the gross proceeds of any Common Stock sold through Goldman under the Equity Distribution Agreement. The Company terminated the Equity Distribution Agreement in August 2023. In August 2023, the Company entered into an Open Market Sales Agreement (the "Sales Agreement") with Jefferies LLC ("Jefferies") to sell shares of the Company’s common stock up to $125.0 million, from time to time, through an “at the market” equity offering program under which Jefferies will act as sales agent. As of December 31, 2023, the Company has made no sales pursuant to the Sales Agreement. In December 2023, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with Goldman and J.P. Morgan Securities LLC, to sell 83.3 million shares of the Company's common stock. The Company received net proceeds of approximately $118.1 million. In March 2024, the Company entered into a five-year term loan facility agreement with Hercules Capital, Inc. to secure debt financing for up to $175 million, available in four tranches. Since its inception, the Company has incurred significant operating losses and negative operating cash flows. As of December 31, 2023, the Company had an accumulated deficit of $4.3 billion. During the twelve months ended December 31, 2023, the Company incurred a net loss of $211.9 million and used $235.0 million of cash in operations. As of December 31, 2023, the Company had cash and cash equivalents of $221.8 million. In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the Company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that these consolidated financial statements are issued. The Company's history of recurring operating losses and negative operating cash flows, its expectation to generate operating losses and negative operating cash flows, and the need for additional funding to support its planned operations raise substantial doubt regarding the Company’s ability to continue as a going concern for a period of one year after the date that these consolidated financial statements are issued. Management's plans to alleviate the conditions that raise substantial doubt include controlling spending, executing on commercial launch plans, and exploring additional financing options. Management has concluded the likelihood that its plan to successfully obtain sufficient funding from one or more of these sources, or adequately reduce expenditures, while reasonably possible, is less than probable. Accordingly, the Company has concluded that substantial doubt exists about the Company’s ability to continue as a going concern for a period of at least 12 months from the date of issuance of these consolidated financial statements. The Company has based the estimated cash needs on assumptions that may prove to be wrong, and its operating plan may change as a result of many factors currently unknown to it. As a result, the Company could deplete its capital resources sooner than it currently expects. Along with the Company's revenue from product sales, the Company expects to finance its future cash needs through the issuance of equity, or debt, or other alternative means. If the Company is unable to obtain funding on a timely basis, or if revenues from product sales are less than it has projected, the Company may be required to further revise its business plan and strategy, which may result in the Company significantly curtailing, delaying or discontinuing one or more of its research or development programs or the commercialization of any products or may result in the Company being unable to expand its operations or otherwise capitalize on its business opportunities. As a result, the Company's business, financial condition and results of operations could be materially affected. The accompanying financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described above.