Condensed unconsolidated financial information of Avantor, Inc. - statements of cash flows (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash flows from investing activities:
Net cash provided by (used in) investing activities	$ (130.5)	$ 438.9	$ (143.7)
Cash flows from financing activities:
Shares repurchased to satisfy employee tax obligations for vested stock-based awards	(5.6)	(8.6)	(13.7)
Net cash (used in) provided by financing activities	(409.4)	(1,281.2)	(843.7)
Cash, cash equivalents and restricted cash, beginning of year	264.7	287.7	396.9
Cash, cash equivalents and restricted cash, end of year	368.3	264.7	287.7
Unconsolidated Avantor, Inc
Cash flows from investing activities:
Contribution from (to) unconsolidated subsidiaries	0.5	(60.6)	(4.6)
Net cash provided by (used in) investing activities	0.5	(60.6)	(4.6)
Cash flows from financing activities:
Proceeds received from exercise of stock options	5.1	69.2	18.3
Shares repurchased to satisfy employee tax obligations for vested stock-based awards	(5.6)	(8.6)	(13.7)
Net cash (used in) provided by financing activities	(0.5)	60.6	4.6
Net change in cash and cash equivalents	0.0	0.0	0.0
Cash, cash equivalents and restricted cash, beginning of year	0.0	0.0	0.0
Cash, cash equivalents and restricted cash, end of year	$ 0.0	$ 0.0	$ 0.0

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Amount of cash and cash equivalent, and cash and cash equivalent restricted to withdrawal or usage; attributable to continuing operation. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate.

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Amount of cash inflow (outflow) from investing activity, including, but not limited to, discontinued operation. Investing activity includes, but is not limited to, making and collecting loan, acquiring and disposing of debt and equity instruments, property, plant, and equipment, and other productive assets.

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The net cash outflow or inflow associated with the acquisition or sale of a business segment during the period.

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