Name:	regn_Amountofmilestonepaymentsthatmaybereceivedrelatingtomarketingapproval
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Future development milestone payment the Company is eligible to receive.

No definition available.

Name:	regn_FuturedevelopmentmilestonepaymenttheCompanyiseligibletoreceive
Namespace Prefix:	regn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The maximum percentage of outstanding shares of the Company's Class A Stock and Common Stock that may be acquired under the 'standstill' provisions, in effect after the specified date.

No definition available.

Name:	regn_MaximumPercentageOfOutstandingSharesThatMayBeAcquiredUnderStandstillProvisions
Namespace Prefix:	regn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Number of development milestone payments the Company received

No definition available.

Name:	regn_NumberofdevelopmentmilestonepaymentstheCompanyreceived
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

potential opt-in payment the Company is eligible to receive from Bayer HealthCare.

No definition available.

Name:	regn_Optinpayment
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Percentage of development cost for the territory outside the United States previously required to be paid for under the collaboration.

No definition available.

Name:	regn_PercentageofdevelopmentcostfortheterritoryoutsidetheUnitedStatespreviouslyrequiredtobepaidforunderthecollaboration
Namespace Prefix:	regn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of development milestone payments Bayer HealthCare is obligated to reimburse the Company for payments that the Company makes to Sanofi related to the Company's acquisition of rights to antibodies targeting the PDGF family of receptors.

No definition available.

Name:	regn_Percentageofdevelopmentmilestonepaymentstobereimbursed
Namespace Prefix:	regn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of global development cost to be paid by the collaboration partner under the collaboration

No definition available.

Name:	regn_Percentageofglobaldevelopmentcosttobepaidbythecollaborationpartnerunderthecollaboration
Namespace Prefix:	regn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Substantive milestone payment from Collaborators to the Company under certain defined circumstances.

No definition available.

Name:	regn_SubstantiveMilestonePaymentToCompany
Namespace Prefix:	regn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Carrying amount as of the balance sheet date, net of allowance for doubtful accounts, of account and note receivables due from other than related parties.

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 210.5-02.3-4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Period Type:	instant

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.

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

Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 13.A.4(a).Q1)
-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 13
-Section A

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Cash received from collaborators during the current period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3536-108585