XML 47 R36.htm IDEA: XBRL DOCUMENT
v3.25.3

Acquisitions, Research Collaborations and Licensing Agreements - Narrative (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended | 15 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Oct. 31, 2025 USD ($) | Sep. 30, 2025 USD ($) | Mar. 31, 2025 USD ($) | Sep. 30, 2024 USD ($) | Jul. 31, 2024 USD ($) aqua_facility | Mar. 31, 2024 USD ($) | Dec. 31, 2025 USD ($) | Sep. 30, 2025 USD ($) | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) | May 31, 2025 USD ($) | Dec. 31, 2024 USD ($) | Feb. 29, 2024 USD ($)
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  | $ 4,234.0 | $ 5,862.0 | $ 11,903.0 | $ 13,354.0 |  |  |  |
Property, plant and equipment, net |  | $ 25,639.0 |  |  |  |  |  | 25,639.0 |  | 25,639.0 |  | $ 25,639.0 |  | $ 23,779.0 |
Intangible assets |  | 15,313.0 |  |  |  |  |  | 15,313.0 |  | 15,313.0 |  | 15,313.0 |  | $ 16,370.0 |
Elanco Animal Health Incorporated Aqua Business |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash paid for acquisition of business |  |  |  |  | $ 1,300.0 |  |  |  |  |  |  |  |  |  |
Aqua manufacturing facilities | aqua_facility |  |  |  |  | 2,000,000 |  |  |  |  |  |  |  |  |  |
Verona Pharma plc | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred, asset acquisition | $ 10,500.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
LaNova Medicines Ltd |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  | 300.0 |  | 300.0 |  |  |  |  |
HRS-5346 , Jiangsu Hengrui Pharmaceuticals Co., Ltd. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  | 200.0 |  |  |  |  |
Jiangsu Hengrui Pharmaceuticals Co., Ltd. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Future contingent developmental milestone payments (up to) |  |  |  |  |  |  |  |  |  |  |  |  | $ 92.5 |  |
Future regulatory milestone payments (up to) |  |  |  |  |  |  |  |  |  |  |  |  | 177.5 |  |
Maximum aggregate sales-based milestone payments |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,500.0 |  |
WuXi Vaccines' facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred, asset acquisition |  |  | $ 437.0 |  |  |  |  |  |  |  |  |  |  |  |
WuXi Vaccines' facility | Asset under Construction |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment, net |  |  | $ 759.0 |  |  |  |  |  |  |  |  |  |  |  |
MK-1045/CN201, Curon Biopharmaceutical |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  | 750.0 |  | 750.0 |  |  |  |
Consideration transferred, asset acquisition |  |  |  | $ 700.0 |  |  |  |  |  |  |  |  |  |  |
Future contingent developmental milestone payments (up to) |  |  |  | 300.0 |  |  |  |  | 300.0 |  | 300.0 |  |  |  |
Future regulatory milestone payments (up to) |  |  |  | 300.0 |  |  |  |  | 300.0 |  | 300.0 |  |  |  |
Eyebiotech Limited |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  | 1,350.0 |  | 1,350.0 |  |  |  |
Consideration transferred, asset acquisition |  |  |  |  | $ 1,200.0 |  |  |  |  |  |  |  |  |  |
Future contingent developmental milestone payments (up to) |  |  |  |  | 1,000.0 |  |  |  |  |  |  |  |  |  |
Future regulatory milestone payments (up to) |  |  |  |  | 200.0 |  |  |  |  |  |  |  |  |  |
Maximum aggregate sales-based milestone payments |  |  |  |  | 500.0 |  |  |  |  |  |  |  |  |  |
Asset acquisition, transaction costs |  |  |  |  | 207.0 |  |  |  |  |  |  |  |  |  |
Developmental milestone payment triggered and paid |  |  |  |  |  |  |  |  | 100.0 | 100.0 | 100.0 | 200.0 |  |  |
Net assets acquired |  |  |  |  | $ 21.0 |  |  |  |  |  |  |  |  |  |
Harpoon Therapeutics, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  |  | 656.0 |  |  |  |
Consideration transferred, asset acquisition |  |  |  |  |  | $ 765.0 |  |  |  |  |  |  |  |  |
Asset acquisition, transaction costs |  |  |  |  |  | $ 56.0 |  |  |  |  |  |  |  |  |
Net assets acquired |  |  |  |  |  |  |  |  |  |  | 165.0 |  |  |  |
Forecast | sac-TMT |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development arrangement, contract to perform for others, compensation earned | 700.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dr. Falk Pharma | Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  | $ 150.0 |  |  |  |  |  |  |  |
Third-Party | MK-1045/CN201, Curon Biopharmaceutical |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net assets acquired |  |  |  | $ 128.0 |  |  |  |  | $ 128.0 |  | $ 128.0 |  |  |  |
Alteogen Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate, regulatory milestones payments, maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 51.0
Sales milestone payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,000.0
Sales based royalty percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.00%
Collaborative arrangement, rights and obligations, probable contingent payments |  | 680.0 |  |  |  |  |  |  |  |  |  |  |  |  |
Alteogen Inc. | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Keytruda Qlex |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities resulting milestone payments |  | 705.0 |  |  |  |  |  | 705.0 |  | 705.0 |  | 705.0 |  |  |
Intangible assets |  | $ 705.0 |  |  |  |  |  | $ 705.0 |  | $ 705.0 |  | $ 705.0 |  |  |
Alteogen Inc. | Subsequent Event | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Keytruda Qlex |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities resulting milestone payments | $ 25.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition Aqua Manufacturing Facilities + References No definition available. + Details
Name: | mrk_AquaManufacturingFacilities
Namespace Prefix: | mrk_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Asset Acquisition, Assets Acquired And Liabilities Assumed, Net + References No definition available. + Details
Name: | mrk_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Asset Acquisition, Maximum Aggregate Contingent Development, Regulatory, and Sales-Based-Related Payments + References No definition available. + Details
Name: | mrk_AssetAcquisitionMaximumAggregateContingentDevelopmentRegulatoryAndSalesBasedRelatedPayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Asset Acquisition, Maximum Aggregate Contingent Development-Related Payments + References No definition available. + Details
Name: | mrk_AssetAcquisitionMaximumAggregateContingentDevelopmentRelatedPayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Asset Acquisition, Maximum Aggregate Regulatory Milestone Payments + References No definition available. + Details
Name: | mrk_AssetAcquisitionMaximumAggregateRegulatoryMilestonePayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Asset Acquisition, Maximum Aggregate Sales-Based Milestone Payments + References No definition available. + Details
Name: | mrk_AssetAcquisitionMaximumAggregateSalesBasedMilestonePayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Asset Acquisition, Milestone Payment Triggered and Paid, Development + References No definition available. + Details
Name: | mrk_AssetAcquisitionMilestonePaymentTriggeredAndPaidDevelopment
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Collaborative Arrangement, Rights And Obligations, Liabilities Resulting From Milestone Payments + References No definition available. + Details
Name: | mrk_CollaborativeArrangementRightsAndObligationsLiabilitiesResultingFromMilestonePayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Collaborative Arrangement, Rights And Obligations, Maximum Aggregate Regulatory Milestone Payments + References No definition available. + Details
Name: | mrk_CollaborativeArrangementRightsAndObligationsMaximumAggregateRegulatoryMilestonePayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Collaborative Arrangement, Rights And Obligations, Maximum Aggregate Sales-Based Milestone Payments + References No definition available. + Details
Name: | mrk_CollaborativeArrangementRightsAndObligationsMaximumAggregateSalesBasedMilestonePayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Collaborative Arrangement, Rights And Obligations, Probable Contingent Payments + References No definition available. + Details
Name: | mrk_CollaborativeArrangementRightsAndObligationsProbableContingentPayments
Namespace Prefix: | mrk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Collaborative Arrangement, Rights And Obligations, Royalty Percentage On Sales + References No definition available. + Details
Name: | mrk_CollaborativeArrangementRightsAndObligationsRoyaltyPercentageOnSales
Namespace Prefix: | mrk_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of consideration transferred in asset acquisition. Includes, but is not limited to, cash, liability incurred by acquirer, and equity interest issued by acquirer. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 55 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479908/805-50-55-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480060/805-50-25-1 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 30 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480027/805-50-30-1 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 30 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480027/805-50-30-2 + Details
Name: | us-gaap_AssetAcquisitionConsiderationTransferred
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of transaction cost incurred as part of consideration transferred in asset acquisition. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 55 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479908/805-50-55-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480060/805-50-25-1 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 30 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480027/805-50-30-1 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 50 -Name Accounting Standards Codification -Section 30 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480027/805-50-30-2 + Details
Name: | us-gaap_AssetAcquisitionConsiderationTransferredTransactionCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-4 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 47 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-47 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-5 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (f)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(1)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(1)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-2 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-2 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (f)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-3 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4 Reference 22: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-4 Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 31: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 32: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 33: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 34: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 35: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 36: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 37: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 38: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 39: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 40: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 41: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 42: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 + Details
Name: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482686/350-30-45-1 + Details
Name: | us-gaap_IntangibleAssetsNetExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 41 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-41 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-13 + Details
Name: | us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 10 -Topic 360 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482099/360-10-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 852 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481372/852-10-55-10 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(8)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 360 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478451/942-360-50-1 + Details
Name: | us-gaap_PropertyPlantAndEquipmentNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of compensation earned (contract income) under a research and development arrangement accounted for as a contract to perform research and development for others. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 730 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483041/730-20-50-1 + Details
Name: | us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of expense for research and development. Includes, but is not limited to, cost for computer software product to be sold, leased, or otherwise marketed and writeoff of research and development assets acquired in transaction other than business combination or joint venture formation or both. Excludes write-down of intangible asset acquired in business combination or from joint venture formation or both, used in research and development activity. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147476153/220-40-55-18 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147476153/220-40-55-14 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 48 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-48 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 985 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481283/985-20-50-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 730 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482916/730-10-50-1 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 912 -SubTopic 730 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479532/912-730-25-1 + Details
Name: | us-gaap_ResearchAndDevelopmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=mrk_ElancoAnimalHealthIncorporatedAquaBusinessMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_VeronaPharmaPlcMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_LaNovaMedicinesLtdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_HRS5346JiangsuHengruiPharmaceuticalsCo.Ltd.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_JiangsuHengruiPharmaceuticalsCo.Ltd.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_WuXiVaccinesFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_AssetUnderConstructionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_MK1045CN201CuronBiopharmaceuticalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_EyebiotechLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_HarpoonTherapeuticsInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AssetAcquisitionAxis=mrk_SacTMTMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CounterpartyNameAxis=mrk_Dr.FalkPharmaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CounterpartyNameAxis=mrk_ThirdPartyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CounterpartyNameAxis=mrk_AlteogenInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TypeOfArrangementAxis=us-gaap_CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=mrk_KeytrudaQlexMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |