(Loss) Earnings Per Share	9 Months Ended
Sep. 30, 2017
Earnings Per Share [Abstract]
(Loss) Earnings Per Share	(Loss) Earnings Per Share Basic (loss) earnings per share is computed by dividing consolidated net loss attributable to The Medicines Company by the weighted average number of shares of common stock outstanding during the period, excluding unvested restricted common shares. The potentially dilutive effect of the Company’s stock options, unvested restricted common stock, stock purchase warrants, and convertible senior notes due 2017 (which matured on June 1, 2017) and 2022 on earnings per share is computed under the treasury stock method. In addition, the Company analyzes the potential dilutive effect of the convertible senior notes due 2023 on earnings per share under the “if converted” method, in which it is assumed that the outstanding security converts into common stock at the beginning of the period. For periods of net income when the effects are not anti-dilutive, diluted earnings per share is computed by dividing the net income attributable to The Medicines Company by the weighted average number of shares outstanding and the impact of all potential dilutive common shares, consisting primarily of stock options, unvested restricted common stock, shares issuable upon conversion of convertible senior notes due 2017, 2022 and 2023 and stock purchase warrants. For periods of net loss from continuing operations, diluted loss per share is calculated similar to basic loss per share as the effect of including all potentially dilutive common share equivalents is anti-dilutive. Due to the periods of net loss from continuing operations attributable to The Medicines Company, the calculation of diluted loss per share for the three and nine months ended September 30, 2017 excluded 10,703,826 and 13,312,289, respectively, of potentially dilutive stock options, warrants, restricted common shares, and shares issuable upon conversion of the 2017, 2022 and 2023 Notes as their inclusion would have an anti-dilutive effect. The calculation of diluted loss per share for the three and nine months ended September 30, 2016 excluded 3,930,938 and 3,109,274, respectively, of potentially dilutive stock options, stock purchase warrants, restricted common shares, and shares issuable upon conversion of the 2017, 2022 and 2023 Notes as their inclusion would have an anti-dilutive effect.

(Loss) Earnings Per Share

Basic (loss) earnings per share is computed by dividing consolidated net loss attributable to The Medicines Company by the weighted average number of shares of common stock outstanding during the period, excluding unvested restricted common shares. The potentially dilutive effect of the Company’s stock options, unvested restricted common stock, stock purchase warrants, and convertible senior notes due 2017 (which matured on June 1, 2017) and 2022 on earnings per share is computed under the treasury stock method. In addition, the Company analyzes the potential dilutive effect of the convertible senior notes due 2023 on earnings per share under the “if converted” method, in which it is assumed that the outstanding security converts into common stock at the beginning of the period.

For periods of net income when the effects are not anti-dilutive, diluted earnings per share is computed by dividing the net income attributable to The Medicines Company by the weighted average number of shares outstanding and the impact of all potential dilutive common shares, consisting primarily of stock options, unvested restricted common stock, shares issuable upon conversion of convertible senior notes due 2017, 2022 and 2023 and stock purchase warrants.

For periods of net loss from continuing operations, diluted loss per share is calculated similar to basic loss per share as the effect of including all potentially dilutive common share equivalents is anti-dilutive. Due to the periods of net loss from continuing operations attributable to The Medicines Company, the calculation of diluted loss per share for the three and nine months ended September 30, 2017 excluded 10,703,826 and 13,312,289, respectively, of potentially dilutive stock options, warrants, restricted common shares, and shares issuable upon conversion of the 2017, 2022 and 2023 Notes as their inclusion would have an anti-dilutive effect.

The calculation of diluted loss per share for the three and nine months ended September 30, 2016 excluded 3,930,938 and 3,109,274, respectively, of potentially dilutive stock options, stock purchase warrants, restricted common shares, and shares issuable upon conversion of the 2017, 2022 and 2023 Notes as their inclusion would have an anti-dilutive effect.