Financial Instruments and Risk Management (Effect of Derivative Instruments on the Condensed Consolidated Balance Sheets Fair Value of Derivative Instruments Derivatives Designated As Hedging Instruments) (Details) € in Millions, ¥ in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 EUR (€)	Sep. 30, 2025 JPY (¥)	Sep. 30, 2025 USD ($)	Dec. 31, 2024 EUR (€)	Dec. 31, 2024 JPY (¥)	Dec. 31, 2024 USD ($)
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax	$ (2.1)	$ 0.9	$ 7.2	$ 14.3
Net Investment Hedging
Derivatives, Fair Value [Line Items]
Long-term debt					€ 2,850.0	¥ 40,000
Notional amount of derivative					€ 2,850.0	¥ 40,000		€ 2,850.0	¥ 40,000
Net Investment Hedging \| Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	1.2	(4.3)	(3.4)	9.7
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax	1.2		2.3
Net Investment Hedging \| Foreign currency forward contracts \| Not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	18.0	(168.4)	(331.4)	(6.3)
Net Investment Hedging \| Interest rate swaps \| Interest Expense
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	1.9	(21.7)	(58.2)	(11.7)
Cash Flow Hedging \| Interest rate swaps \| Interest Expense
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	(0.9)	(1.2)	(2.8)	(3.7)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax	$ (1.2)	$ (1.6)	$ (3.6)	$ (4.8)
2027 Euro Senior Notes
Derivatives, Fair Value [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					1.362%	1.362%	1.362%
2027 Euro Senior Notes \| Senior Notes
Derivatives, Fair Value [Line Items]
Long-term debt							$ 1,012.7			$ 899.4
2027 Euro Senior Notes \| Net Investment Hedging
Derivatives, Fair Value [Line Items]
Long-term debt \| €					€ 850.0
Notional amount of derivative \| €					€ 850.0			850.0
2028 Euro Senior Notes \| Senior Notes
Derivatives, Fair Value [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					3.125%	3.125%	3.125%
2028 Euro Senior Notes \| Net Investment Hedging
Derivatives, Fair Value [Line Items]
Long-term debt \| €					€ 750.0
Notional amount of derivative \| €					€ 750.0			750.0
2032 Euro Senior Notes \| Senior Notes
Derivatives, Fair Value [Line Items]
Long-term debt							$ 1,550.6			1,376.2
Debt Instrument, Interest Rate, Stated Percentage					1.908%	1.908%	1.908%
2032 Euro Senior Notes \| Net Investment Hedging
Derivatives, Fair Value [Line Items]
Long-term debt \| €					€ 1,250.0
Notional amount of derivative \| €					€ 1,250.0			€ 1,250.0
YEN Term Loan
Derivatives, Fair Value [Line Items]
Long-term debt							$ 0.0			$ 254.4
YEN Term Loan \| Net Investment Hedging
Derivatives, Fair Value [Line Items]
Long-term debt \| ¥						¥ 40,000
Notional amount of derivative \| ¥						¥ 40,000			¥ 40,000

Viatris Inc 10-Q