Financial instruments and fair value measurements - Schedule of gross amounts and fair values of debt instruments (Details) - USD ($) $ in Millions	Sep. 30, 2026	Jul. 14, 2026	Dec. 31, 2025
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	$ 3,699.7		$ 3,967.9
Fair value	3,612.8		3,910.1
Senior secured credit facilities: | Euro term loans B-6 | Euro
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	0.0	$ 427.1	645.2
Fair value	0.0		652.0
Senior secured credit facilities: | Euro term loans B-7 | Euro
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	423.7		0.0
Fair value	426.6		0.0
Senior secured credit facilities: | Euro term loans A-1 | Euro
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	442.7		469.2
Fair value	442.7		445.5
Notes | 3.875% unsecured notes
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	800.0		800.0
Fair value	749.0		765.9
Notes | 3.875% Euro unsecured notes
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	454.0		469.2
Fair value	453.2		470.2
Notes | 4.625% unsecured notes
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	1,550.0		1,550.0
Fair value	1,512.0		1,542.2
Finance lease liabilities
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	24.6		26.9
Fair value	24.6		26.9
Other Debt
Estimated Fair Value Of Financial Instruments [Line Items]
Gross amount	4.7		7.4
Fair value	$ 4.7		$ 7.4