(Loss) Earnings per Share (Details) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2013 Convertible Debt [Member]	Jun. 30, 2014 Convertible Debt [Member]	Jun. 30, 2013 Convertible Debt [Member]	Jun. 30, 2012 Convertible Debt [Member]	Jun. 30, 2014 Option [Member]	Jun. 30, 2013 Option [Member]	Jun. 30, 2014 Option [Member]	Jun. 30, 2013 Option [Member]	Jun. 30, 2014 Restricted Stock [Member]	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2014 Restricted Stock [Member]	Jun. 30, 2013 Restricted Stock [Member]
Schedule of Earnings per Share Basic and Diluted [Line Items]
Net (loss) income attributable to The Medicines Company	$ (5,157,000)	$ 18,094,000	$ (10,153,000)	$ 6,521,000
Weighted average common shares outstanding, basic (shares)	64,400,000	55,553,000	64,277,000	54,804,000
Plus: net effect of dilutive stock options, restricted common shares and shares issuable upon conversion of Notes (shares)	0	4,708,000	0	4,350,000
Weighted average common shares outstanding, diluted (shares)	64,400,000	60,261,000	64,277,000	59,154,000
(Loss) income per share attributable to The Medicines Company, basic (USD per share)	$ (0.08)	$ 0.33	$ (0.16)	$ 0.12
(Loss) income per share attributable to The Medicines Company, diluted (USD per share)	$ (0.08)	$ 0.30	$ (0.16)	$ 0.11
Antidilutive common stock shares excluded from computation of earnings per share						1,626,162	767,688	1,251,775		1,426,987	2,707,156	1,777,605	2,706,534	233,761	0	303,829	0
Convertible senior notes (due 2017)	$ 241,304,000		$ 241,304,000		$ 236,088,000				$ 275,000,000
Interest rate									1.375%
Shares exercisable upon conversion	9,800,000		9,800,000
Strike price (USD per share)	$ 34.2		$ 34.2