Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

+ Details

Name:	us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Repayment received or receivable for expenses incurred on behalf of a client or customer, other than those reimbursements received by landlords from tenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 45
-Section 45
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=51671805&loc=d3e60722-111653

+ Details

Name:	us-gaap_ReimbursementRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=mdco_AccountingStandardsUpdate201503Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=mdco_ConvertibleSeniorNotesCurrentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=mdco_ConvertibleSeniorNotesNoncurrentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reimbursement by government	$ 6.3	$ 3.2
Accounting Standards Update 2015-03 [Member] \| Current convertible senior notes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issuance costs			$ 2.4
Accounting Standards Update 2015-03 [Member] \| Noncurrent convertible senior notes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issuance costs			$ 9.0