Debt - other information (Details) € in Millions			1 Months Ended	3 Months Ended		9 Months Ended
Debt - other information (Details) € in Millions	Apr. 02, 2024 USD ($)	Apr. 01, 2024 USD ($)	Oct. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Oct. 31, 2025 EUR (€)	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Oct. 25, 2022 USD ($)
Debt Instrument [Line Items]
Interest income				$ 11,900,000	$ 26,800,000	$ 30,800,000	$ 62,600,000
Facility limit											$ 400,000,000.0
Gross amount				$ 3,874,200,000		3,874,200,000				$ 4,077,800,000
Repayments of long-term debt						$ 477,300,000	$ 585,000,000.0
Debt covenants draw trigger percentage				35.00%
Interest rate swaps
Debt Instrument [Line Items]
Derivative, notional amount									$ 750,000,000.0
Subsequent Event \| Interest rate swaps
Debt Instrument [Line Items]
Derivative, notional amount			$ 100,000,000.0
Amended Revolving Credit Facility Mature In October 2030 \| Subsequent Event \| Revolving credit facility
Debt Instrument [Line Items]
Revolving credit facility, additional borrowing capacity			425,000,000.0
Revolving credit facility, maximum borrowing capacity			$ 1,400,000,000
Receivables facility
Debt Instrument [Line Items]
Interest terms						0.80%
Gross amount				$ 192,700,000		$ 192,700,000				125,000,000.0
Receivables facility \| Asset Not Pledged as Collateral
Debt Instrument [Line Items]
Amount pledged as collateral				500,600,000		$ 500,600,000
Senior secured credit facilities: \| U.S. dollar term loans B-6
Debt Instrument [Line Items]
Interest terms	2.00%	2.25%				2.00%
Gross amount	$ 772,400,000	$ 772,400,000		80,800,000		$ 80,800,000				86,600,000
Notes \| 2.625% secured notes
Debt Instrument [Line Items]
Gross amount				293,200,000		$ 293,200,000				$ 672,600,000
Repayments of long-term debt				$ 457,400,000
Senior Loans \| Term Loan Mature In October 2032 \| Subsequent Event
Debt Instrument [Line Items]
Interest terms			1.50%
Debt instrument, face amount \| €								€ 400.0
Senior Loans \| Term Loan Mature In October 2030 \| Subsequent Event
Debt Instrument [Line Items]
Interest terms			2.50%
Debt instrument, face amount \| €								€ 550.0

Avantor, Inc. 10-Q