| Cover Page Cover Page | Oct. 30, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Oct. 30, 2019 |
| Entity Registrant Name | MEDICINES CO /DE |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 000-31191 |
| Entity Tax Identification Number | 04-3324394 |
| Entity Address, Address Line One | 8 Sylvan Way |
| Entity Address, City or Town | Parsippany |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 07054 |
| City Area Code | 973 |
| Local Phone Number | 290-6000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | MDCO |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001113481 |
| Amendment Flag | false |
