Description of Business and Basis of Presentation	12 Months Ended
Description of Business and Basis of Presentation	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation Description of Business—Insmed is a global biopharmaceutical company on a mission to transform the lives of patients with serious and rare diseases. The Company's first commercial product, ARIKAYCE (amikacin liposome inhalation suspension), received accelerated approval in the United States (US) on September 28, 2018 for the treatment of refractory Mycobacterium avium complex (MAC) lung disease as part of a combination antibacterial drug regimen for adult patients with limited or no alternative treatment options. MAC lung disease is a rare and often chronic infection that can cause irreversible lung damage and can be fatal. The Company's clinical-stage pipeline includes INS1007 and INS1009. INS1007 is a novel oral, reversible inhibitor of dipeptidyl peptidase 1 (DPP1) with therapeutic potential in non-cystic fibrosis (non-CF) bronchiectasis and other inflammatory diseases. INS1009 is an inhaled formulation of a treprostinil prodrug that may offer a differentiated product profile for rare pulmonary disorders, including pulmonary arterial hypertension (PAH). The Company was incorporated in the Commonwealth of Virginia on November 29, 1999 and its principal executive offices are located in Bridgewater, New Jersey. The Company has legal entities in the US, Ireland, Germany, France, the United Kingdom (UK), the Netherlands, Bermuda and Japan. The Company had $495.1 million in cash and cash equivalents as of December 31, 2018 and reported a net loss of $324.3 million for the year ended December 31, 2018. Historically, the Company has funded its operations through public offerings of equity securities and debt financings. To date, the Company has not generated significant revenue from ARIKAYCE. The Company commenced commercial shipments in October 2018. The Company expects to continue to incur operating losses while funding commercial launch efforts for ARIKAYCE, research and development (R&D) activities, regulatory submissions outside the US, and selling, general and administrative (SG&A) expenses. The Company expects its future cash requirements to be substantial, and it may need to raise additional capital to fund operations, including the commercialization of ARIKAYCE and additional clinical trials related to ARIKAYCE, to develop INS1007 and INS1009 and to develop, acquire, in-license or co-promote other products that address orphan or rare diseases. The source, timing and availability of any future financing or other transaction will depend principally upon continued progress in the Company’s commercial, regulatory and development activities. Any equity or debt financing will also be contingent upon equity and debt market conditions and interest rates at the time. If the Company is unable to obtain sufficient additional funds when required, the Company may be forced to delay, restrict or eliminate all or a portion of its development programs or commercialization efforts. The Company believes it currently has sufficient funds to meet its financial needs for at least the next 12 months. Basis of Presentation—The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Insmed Limited, Celtrix Pharmaceuticals, Inc., Insmed Holdings Limited, Insmed Ireland Limited, Insmed France SAS, Insmed Germany GmbH, Insmed Netherlands B.V., Insmed Bermuda Limited and Insmed Godo Kaisha. All intercompany transactions and balances have been eliminated in consolidation and certain prior year amounts have been restated to conform to the current year presentation. In the prior year, accrued compensation was presented within the accrued expense line in the consolidated balance sheet. In the current year, accrued compensation is presented as a discrete line on the face of the consolidated balance sheet.