Benefit Plans, Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	$ 7.7	$ 6.8	$ 8.1
Interest cost	10.5	14.0	13.0
Expected return on plan assets	(20.1)	(18.2)	(20.2)
Amortization of prior service cost	0.0	0.0	0.0
Recognized net actuarial (gain) loss	13.9	10.1	10.7
Settlement/curtailment (gain) loss	6.4	(0.1)	4.4
Net periodic benefit cost	18.4	12.6	16.0
Post-Retirement Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	0.2	0.2	0.2
Interest cost	0.2	0.2	0.2
Expected return on plan assets	0.0	0.0	0.0
Amortization of prior service cost	0.0	0.0	(0.9)
Recognized net actuarial (gain) loss	(0.9)	(0.9)	(0.8)
Settlement/curtailment (gain) loss	0.0	0.0	0.0
Net periodic benefit cost	$ (0.5)	$ (0.5)	$ (1.3)