Benefit Plans, Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 6.8	$ 8.1	$ 7.9
Interest cost	14.0	13.0	12.6
Expected return on plan assets	(18.2)	(20.2)	(18.7)
Amortization of prior service cost	0.0	0.0	0.0
Recognized net actuarial (gain) loss	10.1	10.7	10.8
Settlement/curtailment loss	(0.1)	4.4	0.0
Net periodic benefit cost	12.6	16.0	12.6
Post-Retirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0.2	0.2	0.3
Interest cost	0.2	0.2	0.3
Expected return on plan assets	0.0	0.0	0.0
Amortization of prior service cost	0.0	(0.9)	(3.1)
Recognized net actuarial (gain) loss	(0.9)	(0.8)	(0.3)
Settlement/curtailment loss	0.0	0.0	0.0
Net periodic benefit cost	$ (0.5)	$ (1.3)	$ (2.8)