Share Plans - Share-based compensation expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation	$ 24.9	$ 29.8	$ 20.3
Restricted Stock Units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation	14.6	13.0	12.5
Equity Option
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation	3.7	3.4	3.0
Performance Shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation	$ 6.6	$ 13.4	$ 4.8