Pension and Other Benefits Accumulated and Projected Benefit Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, pension plan with accumulated benefit obligation in excess of plan assets, projected benefit obligation	$ 51.5	$ 49.2
Defined benefit plan, plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	51.5	49.2
Defined benefit plan, plan with accumulated benefit obligation in excess of plan assets, plan assets	46.2	40.5
Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, pension plan with accumulated benefit obligation in excess of plan assets, projected benefit obligation	68.6	67.9
Defined benefit plan, plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	68.6	67.9
Defined benefit plan, plan with accumulated benefit obligation in excess of plan assets, plan assets	0.0	0.0
Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, pension plan with accumulated benefit obligation in excess of plan assets, projected benefit obligation	0.6	0.7
Defined benefit plan, plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	0.0	0.0
Defined benefit plan, plan with accumulated benefit obligation in excess of plan assets, plan assets	$ 0.0	$ 0.0