Loss per Share (Computation of Basic and Diluted Loss Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net loss attributable to The Medicines Company	$ (105,132)	$ (16,736)	$ (146,690)	$ (26,889)
Weighted average common shares outstanding, basic (shares)	67,137	64,534	66,079	64,363
Plus: net effect of dilutive stock options, restricted common shares and shares issuable upon conversion of convertible senior notes due 2017 (shares)	0	0	0	0
Weighted average common shares outstanding, diluted (shares)	67,137	64,534	66,079	64,363
Loss per share attributable to The Medicines Company, basic (USD per share)	$ (1.57)	$ (0.26)	$ (2.22)	$ (0.42)
Loss per share attributable to The Medicines Company, diluted (USD per share)	$ (1.57)	$ (0.26)	$ (2.22)	$ (0.42)