Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Jun. 29, 2012
Schedule of Earnings per Share Basic and Diluted [Line Items]
Net income attributable to The Medicines Company													$ (32,210)	$ 15,512	$ 51,254
Net weighted average common shares outstanding, basic													64,473,000	58,096,000	53,545,000
Plus: net effect of dilutive stock options, warrants, restricted common shares and shares issuable upon conversion of Notes													0	4,556,000	1,801,000
Weighted average common shares outstanding, diluted													64,473,000	62,652,000	55,346,000
Income per common share attributable to The Medicines Company, basic (USD per share)	$ (0.08)	[1],[2]	$ (0.26)	$ (0.08)	[1]	$ (0.08)	$ 0.02	[3]	$ 0.13	$ 0.33	$ (0.21)	[4]	$ (0.50)	$ 0.27	$ 0.96
Income per common share attributable to The Medicines Company, diluted (USD per share)	$ (0.08)	[1],[2]	$ (0.26)	$ (0.08)	[1]	$ (0.08)	$ 0.02	[3]	$ 0.12	$ 0.30	$ (0.21)	[4]	$ (0.50)	$ 0.25	$ 0.93
Convertible senior notes (due 2017)	246,676						236,088						246,676	236,088
Dilutive effect of conversion of the Notes													383,844
Shares exercisable upon conversion	9,800,000												9,800,000			9,800,000
Strike price	$ 34.20												$ 34.20
Dilutive effect of warrants														107,263
Common Stock [Member]
Schedule of Earnings per Share Basic and Diluted [Line Items]
Antidilutive shares excluded from computation of earnings per share													3,910,115	1,335,570	3,171,163
Restricted Stock [Member]
Schedule of Earnings per Share Basic and Diluted [Line Items]
Antidilutive shares excluded from computation of earnings per share													5,791	0	77,235
Convertible Debt [Member]
Schedule of Earnings per Share Basic and Diluted [Line Items]
Convertible senior notes (due 2017)																275,000	$ 275,000
Interest rate																1.375%

[1] Net loss for the second and fourth quarters of 2014 includes impairment charges on product licenses in the amount of $15.1 million and $6.4 million, respectively to cost of sales, as a result of reductions in estimated future cash flows expected to be generated by the acute care generic products as determined by an updated discounted cash flow analysis (Level 3).

[2] In December 2014, the Company entered into a settlement and amendment to the merger agreement with Incline Therapeutics, Inc., which resulted in revisions to certain milestone triggers, a reduction in total milestone payments and the release of the escrow funds to the Company. As a result, net loss for the fourth quarter of 2014 includes $25.7 million in one-time income in connection with the settlement with the former equityholders of Incline related to the representations and warranties included in the merger agreement.

[3] 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.

[4] Net loss for the first quarter of 2013 includes licensing costs of $25.0 million for a transaction with Alnylam on the PCSK9 RNAi hypercholesterolemia program.