Charge for license options related to collaboration

No definition available.

Name:	mrk_ChargeForLicenseOptionsRelatedToCollaboration
Namespace Prefix:	mrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Charge for upfront payment and future option payments related to the formation of a collaboration.

+ References

No definition available.

+ Details

Name:	mrk_ChargeRelatedToCollaborationFormation
Namespace Prefix:	mrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents payments that may be made in the future contingent upon the achievement of regulatory and/or sales milestones as part of a collaborative arrangement.

+ References

No definition available.

+ Details

Name:	mrk_ContingentPaymentsCollaborativeArrangement
Namespace Prefix:	mrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Period of Notice for Agreement Termination

+ References

No definition available.

+ Details

Name:	mrk_PeriodofNoticeforAgreementTermination
Namespace Prefix:	mrk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Total consideration in a collaborative arrangement including upfront and future contingent payments.

+ References

No definition available.

+ Details

Name:	mrk_TotalConsiderationCollaborativeArrangement
Namespace Prefix:	mrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Upfront and milestone payments made to partner as part of collaborative arrangement.

+ References

No definition available.

+ Details

Name:	mrk_UpfrontAndMilestonePaymentsMadeToCollaborativePartner
Namespace Prefix:	mrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

- Definition

The cash outflow to acquire asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

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

- Details

Name:	us-gaap_TypeOfArrangementAxis=mrk_AstraZenecaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisitions, Divestitures, Research Collaborations and License Agreements - Collaborative Arrangements Narrative (Details) - USD ($) $ in Millions	1 Months Ended				3 Months Ended	9 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2017	Jul. 31, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Charge for future payments related to AstraZeneca collaboration license options						$ 750	$ 0
AstraZeneca
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront and milestone payments made to collaborative partner				$ 1,600
Charge for future payments related to AstraZeneca collaboration license options				750
Charge related to collaboration formation					$ 2,350
Maximum amount of contingent payments collaborative arrangement				6,150
Total consideration collaborative arrangement (up to value)				$ 8,500
Period of notice for agreement termination				180 days
AstraZeneca \| Forecast
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Payments to acquire intangible assets	$ 100	$ 400	$ 250