Retirement Plans - Amounts Recognized in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plan
Amortization of:
Net actuarial loss	$ (3.7)	$ (3.1)	$ (1.8)
Amounts arising during the period:
Settlements	0.0	0.0	3.9
Net actuarial gain/(loss)	0.6	1.7	(11.8)
Total	(4.3)	(4.8)	6.1
Other Postretirement Benefit Plan
Amortization of:
Net actuarial loss	(0.1)	0.0	0.0
Amounts arising during the period:
Settlements	0.0	0.0	0.0
Net actuarial gain/(loss)	0.0	(0.2)	(0.6)
Total	$ (0.1)	$ 0.2	$ 0.6