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Collaboration, License, and Other Agreements - Teva Narrative (Details) $ in Millions | Sep. 30, 2020 USD ($)
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Teva |
Disaggregation of Revenue [Line Items] |
Unsatisfied obligation | $ 130.3

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- Definition Unsatisfied Obligation + References No definition available. + Details
Name: | regn_UnsatisfiedObligation
Namespace Prefix: | regn_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition 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. + References No definition available. + Details
Name: | us-gaap_DisaggregationOfRevenueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis=regn_TevaPharmaceuticalsCollaborationAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |