Benefit Plans (Amounts Recognized in Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net actuarial loss (gain)	$ 69.4	$ 73.0
Prior service cost (credit)	0.8	0.9
Total	70.2	73.9
Defined Benefit Plan, Excess of Net Periodic Benefit Cost Over Other Comprehensive Income	0.7	7.1	$ 0.3
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net actuarial loss (gain)	(7.0)	(9.4)
Prior service cost (credit)	(1.0)	(1.7)
Total	(8.0)	(11.1)
Defined Benefit Plan, Excess of Net Periodic Benefit Cost Over Other Comprehensive Income	$ 0.3	$ (1.2)	$ (0.8)