Employee Retirement Plans - Components of net retirement cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Contribution Plan, Cost	$ 2.5	$ 2.5	$ 6.8	$ 6.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0.2	$ 0.1	$ 0.5	$ 0.5