Organization	3 Months Ended
Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization MyoKardia, Inc. (the “Company”) is a clinical-stage biopharmaceutical company pioneering a precision medicine approach to discover, develop and commercialize targeted therapies for the treatment of serious and neglected rare cardiovascular diseases. The Company’s initial focus is on the treatment of heritable cardiomyopathies, a group of rare, genetically driven forms of heart failure that result from biomechanical defects in cardiac muscle contraction. The Company has used its precision medicine platform to generate a robust pipeline of therapeutic programs for the chronic treatment of the two most common forms of heritable cardiomyopathy—hypertrophic cardiomyopathy (“HCM”), and dilated cardiomyopathy (“DCM”). The Company was incorporated on June 8, 2012 in Delaware and its corporate headquarters and operations are located in South San Francisco, California. Liquidity The Company has incurred significant operating losses since inception and has an accumulated deficit of $152.7 million as of March 31, 2018. The Company has relied on its ability to fund its operations through private and public equity financings, and to a lesser extent through a license and collaboration arrangement with its collaboration partner, Sanofi S.A. (“Sanofi”) through its subsidiary, Aventis, Inc. The Company has not yet received regulatory approval to commercialize or sell any product and does not have customers. Management expects operating losses and negative operating cash flows to continue for the foreseeable future. As the Company continues to incur losses, the transition to profitability is dependent upon the successful development, approval, and commercialization of its products and product candidates and the achievement of a level of revenues adequate to support its cost structure. The Company’s ultimate success depends on the outcome of its research and development activities. The Company expects to incur additional losses and negative cash flows for the foreseeable future and it anticipates the need to raise additional capital to fully implement its business plan. The Company intends to raise such capital through the issuance of additional equity, debt and/or strategic alliances with partner companies. As of March 31, 2018, the Company had $259.3 million of cash, cash equivalents and short and long-term investments and management believes the existing cash, cash equivalents and short and long-term investments will be sufficient to meet the Company’s anticipated operating and capital expenditure requirements for the twelve months following the date of this Form 10-Q. Management’s belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding.

1. Organization

MyoKardia, Inc. (the “Company”) is a clinical-stage biopharmaceutical company pioneering a precision medicine approach to discover, develop and commercialize targeted therapies for the treatment of serious and neglected rare cardiovascular diseases. The Company’s initial focus is on the treatment of heritable cardiomyopathies, a group of rare, genetically driven forms of heart failure that result from biomechanical defects in cardiac muscle contraction. The Company has used its precision medicine platform to generate a robust pipeline of therapeutic programs for the chronic treatment of the two most common forms of heritable cardiomyopathy—hypertrophic cardiomyopathy (“HCM”), and dilated cardiomyopathy (“DCM”). The Company was incorporated on June 8, 2012 in Delaware and its corporate headquarters and operations are located in South San Francisco, California.

Liquidity

The Company has incurred significant operating losses since inception and has an accumulated deficit of $152.7 million as of March 31, 2018. The Company has relied on its ability to fund its operations through private and public equity financings, and to a lesser extent through a license and collaboration arrangement with its collaboration partner, Sanofi S.A. (“Sanofi”) through its subsidiary, Aventis, Inc. The Company has not yet received regulatory approval to commercialize or sell any product and does not have customers. Management expects operating losses and negative operating cash flows to continue for the foreseeable future. As the Company continues to incur losses, the transition to profitability is dependent upon the successful development, approval, and commercialization of its products and product candidates and the achievement of a level of revenues adequate to support its cost structure. The Company’s ultimate success depends on the outcome of its research and development activities. The Company expects to incur additional losses and negative cash flows for the foreseeable future and it anticipates the need to raise additional capital to fully implement its business plan. The Company intends to raise such capital through the issuance of additional equity, debt and/or strategic alliances with partner companies. As of March 31, 2018, the Company had $259.3 million of cash, cash equivalents and short and long-term investments and management believes the existing cash, cash equivalents and short and long-term investments will be sufficient to meet the Company’s anticipated operating and capital expenditure requirements for the twelve months following the date of this Form 10-Q. Management’s belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding.