Name:	regn_AmountOfPaymentMadeUponReachingMinimumSalesTarget
Namespace Prefix:	regn_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

The maximum amount of cumulative U.S. sales of EYLEA within the range, which will require the Company to make royalty payments of 4.75%.

No definition available.

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

The minimum amount of cumulative U.S. sales of EYLEA which would require the Company to make payments.

No definition available.

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

Loss Contingency, Number of Litigation Cases

No definition available.

Name:	regn_LossContingencyNumberOfLitigationCases
Namespace Prefix:	regn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Percentage of royalty payment to be made on cumulative U.S. sales of EYLEA over the cumulative sales range, under the terms of the non-exclusive license agreement.

No definition available.

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

Royalty payment percentage to be made on cumulative U.S. sales of EYLEA within the cumulative sales range, under the terms of the non-exclusive license agreement.

No definition available.

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

- Details

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

The total number of new claims filed pertaining to a loss contingency during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_LossContingencyNewClaimsFiledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The total amount of pending claims pertaining to a loss contingency accrual as of the balance sheet date.