Pension and Other Post-Retirement Benefits - Fair Value Pension Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair value of pension plan assets
Assets	$ 462.1	$ 465.5
Short-term investment funds [Member]
Fair value of pension plan assets
Assets	9.1	4.6
Common stock collective funds [Member]
Fair value of pension plan assets
Assets	154.6	223.0
Fixed income collective trust funds [Member]
Fair value of pension plan assets
Assets	289.8	226.0
Real estate investment funds [Member]
Fair value of pension plan assets
Assets	$ 8.6	$ 11.9