Name:	regn_Futurepaymenttobemadeundertermsofamendedlicensingagreement
Namespace Prefix:	regn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Potential agreement term, from the effective date of agreement.

No definition available.

Name:	regn_Licenseagreementterm
Namespace Prefix:	regn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The number of days the licensee must provide advance written notice in order to terminate the licensing agreement.

No definition available.

Name:	regn_NumberOfDaysOfAdvanceWrittenNoticeToTerminateAgreement
Namespace Prefix:	regn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The revenue recognition period (in years) of the up-front payment the Company received under the terms of the amended licensing agreement. This payment was deferred upon receipt and will be recognized as revenue ratably, beginning in mid-2011.

No definition available.

Name:	regn_RecognitionPeriodForAdvancePayment
Namespace Prefix:	regn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets 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 Response)
-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

Name:	us-gaap_DeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_DeferredRevenueArrangementLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Revenue earned during the period relating to consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity.

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(e))
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

Cash received from licensees for license fees 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