Pension and Other Post-Retirement Benefits - Projected and Accumulated Benefit Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligations	$ 380.7	$ 354.1
Fair value of plan assets	321.6	300.4
Pension plans with an accumulated benefit obligation in excess of plan assets
Accumulated benefit obligations	41.7	37.0
Fair value of plan assets	$ 0.0	$ 0.0