Description of Plan (Details) - EBP 004	12 Months Ended
Dec. 31, 2025 USD ($)
EBP, Description of Plan [Line Items]
Minimum annual compensation to total compensation, percentage	2.00%
Participant contribution, pretax, maximum annual compensation to total compensation, percentage	25.00%
Participant contribution, aftertax, maximum annual compensation to total compensation, percentage	25.00%
Participant contribution, maximum contribution to eligible compensation, percentage	25.00%
Employer contribution, matching percentage per US dollar	$ 0.65
Employer contribution, participant compensation matched, percentage	6.00%
Employer contribution, matching percentage	3.90%
Basis spread on variable rate	1.00%
Short term loan, borrowing term	1 year
Receivable from participant, account, primary residence, maximum borrowing term	30 years
Receivable from participant, account, minimum borrowing, amount	$ 500
Receivable from participant, account, maximum borrowing, amount	$ 50,000
Note receivable from participant, account, maximum borrowing, to total account, percentage	50.00%
Minimum
EBP, Description of Plan [Line Items]
Short term loan, borrowing term	1 year
Notes receivable from participants, interest rate	4.25%
Maximum
EBP, Description of Plan [Line Items]
Short term loan, borrowing term	5 years
Notes receivable from participants, interest rate	10.00%

EBP, Employer Contribution, Matching Percentage Per US Dollar

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- Definition

EBP, Note Receivable From Participant, Account, Primary Residence, Maximum Borrowing Term

+ References

No definition available.

+ Details

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- Definition

EBP, Note Receivable From Participant, Short Term Loan, Borrowing Term

+ References

No definition available.

+ Details

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- Definition

EBP, Participant Contribution, Aftertax, Maximum Annual Compensation to Total Compensation, Percentage

+ References

No definition available.

+ Details

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- Definition

EBP, Participant Contribution, Maximum Contribution to Eligible Compensation, Percentage

+ References

No definition available.

+ Details

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- Definition

EBP, Participant Contribution, Pretax, Minimum Annual Compensation to Total Compensation, Percentage

+ References

No definition available.

+ Details

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Namespace Prefix:	mrk_
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- Definition

EBP, Participant Loan, Basis Spread On Variable Rate

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
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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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

+ Details

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of employer matching contribution on eligible participant contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

+ Details

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Period Type:	duration

- Definition

Percentage of participant compensation eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Period Type:	duration

- Definition

Amount of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow to total participant account balance.

+ References

+ Details

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- Definition

Amount of minimum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of maximum pretax annual compensation that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), is permitted to contribute to total pretax annual compensation.

+ References

+ Details

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Namespace Prefix:	us-gaap-ebp_
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Balance Type:	na
Period Type:	duration

- Definition

Interest rate on participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(D)
-Publisher DOL-EBSA

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

+ Details

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- Details

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- Details

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