Employee Retirement Plans - Components of net retirement cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0.1	$ 0.2	$ 0.3	$ 0.4
Defined Contribution Plan, Cost	$ 2.2	$ 1.9	$ 4.3	$ 4.3