Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended			3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Restricted Stock [Member]	Mar. 31, 2012 Restricted Stock [Member]	Mar. 31, 2013 Convertible Debt [Member]	Jun. 30, 2012 Convertible Debt [Member]
Schedule of Earnings per Share Basic and Diluted [Line Items]
Net income attributable to The Medicines Comapny	$ (11,573)	$ 7,571
Weighted average common shares outstanding, basic (shares)	54,047,000	54,037,000
Plus: net effect of dilutive stock options and restricted common shares (shares)	0	1,635,000
Weighted average common shares outstanding, diluted (shares)	54,047,000	55,672,000
Earnings per common share attributable to The Medicines Company, basic (USD per share)	$ (0.21)	$ 0.14
Earnings per common share attributable to The Medicines Company, diluted (USD per share)	$ (0.21)	$ 0.14
Antidilutive common stock shares excluded from computation of earnings per share	2,705,911	3,394,410		407,922	293,940	873,776
Convertible senior notes (due 2017)	$ 228,555		$ 226,109				$ 275,000
Interest rate							1.375%
Shares exercisable upon conversion	9,800,000
Strike price	$ 34.20