Contingencies (Details) $ in Millions		9 Months Ended
	Jul. 22, 2025 case party lawsuit	Sep. 30, 2025 USD ($) case matter	Jul. 28, 2025	Dec. 31, 2024 USD ($)
Loss Contingencies [Line Items]
Number of pending claims	4
Loss contingency, actions taken by plaintiff | party	5
Number of claims subsequently withdrawn	1
Number of shareholder derivative lawsuits filed | lawsuit	2
Amount of legal defense reserves | $		$ 9		$ 7
Fosamax | Federal Court
Loss Contingencies [Line Items]
Number of pending claims		844
Fosamax | Federal Court | Femur Fracture Litigation
Loss Contingencies [Line Items]
Number of claims dismissed		650
Fosamax | New Jersey State Court
Loss Contingencies [Line Items]
Number of pending claims		1,532
Fosamax | California State Court
Loss Contingencies [Line Items]
Number of pending claims		209
Fosamax | Femur Fracture MDL Court | Femur Fracture Litigation
Loss Contingencies [Line Items]
Number of pending claims		844
Minimum percentage of attorneys’ eligible clients to release the company and merck of any liability related to their filed claims			95.00%
Fosamax | Pennsylvania State Court
Loss Contingencies [Line Items]
Number of pending claims		1
Implanon | Int’l
Loss Contingencies [Line Items]
Number of pending claims		7
Implanon | Northern District of Ohio
Loss Contingencies [Line Items]
Number of pending claims		2
Number of unfiled claims		56
Nexplanon | CALIFORNIA
Loss Contingencies [Line Items]
Number of matters involved | matter		1
Nexplanon | Int’l
Loss Contingencies [Line Items]
Number of pending claims		10
Nexplanon/Implanon NXT | Int’l
Loss Contingencies [Line Items]
Number of pending claims		17