Pension and Other Benefits Pension Unfunded Status Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, benefit obligation	$ 120.1	$ 117.3	$ 191.3
Benefit obligation - settlement impact	0.0	(75.5)
Interest cost	3.1	5.4	6.3
Defined benefit plan, benefit obligation, actuarial gain (loss)	7.2	17.1
Defined benefit plan, benefit obligation, benefits paid	(7.5)	(21.0)
Defined benefit plan, plan assets, amount	46.2	40.5	115.3
Plan assets - settlement impact	0.0	(75.5)
Defined benefit plan, plan assets, increase (decrease) for actual return (loss)	3.5	11.4
Defined benefit plan, plan assets, contributions by employer	9.7	10.3
Defined benefit plan, plan assets, benefits paid	(7.5)	(21.0)
Defined benefit plan, funded (unfunded) status of plan	73.9	76.8
Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, benefit obligation	0.6	0.7	0.6
Benefit obligation - settlement impact	0.0	0.0
Interest cost	0.0	0.0	0.0
Defined benefit plan, benefit obligation, actuarial gain (loss)	(0.1)	0.1
Defined benefit plan, benefit obligation, benefits paid	0.0	0.0
Defined benefit plan, plan assets, amount	0.0	0.0	$ 0.0
Plan assets - settlement impact	0.0	0.0
Defined benefit plan, plan assets, increase (decrease) for actual return (loss)	0.0	0.0
Defined benefit plan, plan assets, contributions by employer	0.0	0.0
Defined benefit plan, plan assets, benefits paid	0.0	0.0
Defined benefit plan, funded (unfunded) status of plan	$ 0.6	$ 0.7