Financial instruments and fair value measurements - debt instruments (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Gross amount	$ 3,967.9	$ 4,077.8
Fair value	3,910.1	3,936.5
Secured Debt
Debt Instrument [Line Items]
Gross amount	0.0	125.0
Fair value	0.0	125.0
Senior secured credit facilities: \| Euro term loans B-4 \| Euro
Debt Instrument [Line Items]
Gross amount	0.0	81.6
Fair value	0.0	82.1
Senior secured credit facilities: \| Euro term loans B-5 \| Euro
Debt Instrument [Line Items]
Gross amount	0.0	324.5
Fair value	0.0	326.1
Senior secured credit facilities: \| Euro term loans B-6 \| Euro
Debt Instrument [Line Items]
Gross amount	645.2	0.0
Fair value	652.0	0.0
Senior secured credit facilities: \| U.S. dollar term loans B-6 \| U.S. dollars
Debt Instrument [Line Items]
Gross amount	0.0	86.6
Fair value	0.0	87.2
Senior secured credit facilities: \| Euro term loans A-1 \| Euro
Debt Instrument [Line Items]
Gross amount	469.2	0.0
Fair value	445.5	0.0
Notes \| 2.625% secured notes
Debt Instrument [Line Items]
Gross amount	0.0	672.6
Fair value	0.0	668.4
Notes \| 3.875% unsecured notes
Debt Instrument [Line Items]
Gross amount	800.0	800.0
Fair value	765.9	729.9
Notes \| 3.875% unsecured notes 2
Debt Instrument [Line Items]
Gross amount	469.2	413.9
Fair value	470.2	413.6
Notes \| 4.625 % unsecured notes
Debt Instrument [Line Items]
Gross amount	1,550.0	1,550.0
Fair value	1,542.2	1,480.6
Finance lease liabilities
Debt Instrument [Line Items]
Gross amount	26.9	15.0
Fair value	26.9	15.0
Other
Debt Instrument [Line Items]
Gross amount	7.4	8.6
Fair value	$ 7.4	$ 8.6