Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Common Stock [Member]	Dec. 31, 2012 Common Stock [Member]	Dec. 31, 2011 Common Stock [Member]	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Jun. 29, 2012 Convertible Debt [Member]
Schedule of Earnings per Share Basic and Diluted [Line Items]
Net income attributable to The Medicines Company										$ 15,512	$ 51,254	$ 127,877
Net weighted average common shares outstanding, basic										58,096,000	53,545,000	53,496,000
Plus: net effect of dilutive stock options, warrants, restricted common shares and shares issuable upon conversion of Notes										4,556,000	1,801,000	911,000
Weighted average common shares outstanding, diluted										62,652,000	55,346,000	54,407,000
Income per common share attributable to The Medicines Company, basic (USD per share)	$ 0.02	[1]	$ 0.13	$ 0.33	$ (0.21)	$ 0.39	$ 0.18	$ 0.25	$ 0.14	$ 0.27	$ 0.96	$ 2.39
Income per common share attributable to The Medicines Company, diluted (USD per share)	$ 0.02	[1]	$ 0.12	$ 0.30	$ (0.21)	$ 0.38	$ 0.17	$ 0.25	$ 0.14	$ 0.25	$ 0.93	$ 2.35
Antidilutive shares excluded from computation of earnings per share													1,335,570	3,171,163	6,970,991	77,235	62,473
Convertible senior notes (due 2017)	$ 236,088					$ 226,109				$ 236,088	$ 226,109							$ 275,000
Interest rate																		1.375%
Dilutive effect of conversion of the Notes										1,468,006
Shares exercisable upon conversion	9,800,000									9,800,000
Strike price	$ 34.20									$ 34.20
Dilutive effect of warrants										107,263

[1] (2)Net income for the fourth quarter of 2013 includes a $10.9 million increase related to the progression in development work for IONSYS related to the Company’s Incline acquisition and a tax benefit of $13.6 million from reducing the Company’s deferred tax liabilities associated with the Incline acquisition.