Nature of Operations and Significant Accounting Policies (Reclassified Out of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax impact	$ (82.9)	$ (38.6)	$ (31.3)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total before tax	22.2	17.7	13.6
Tax impact	4.2	3.9	2.9
Total reclassifications for the period	18.0	13.8	10.7
Pension Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs	(0.1)	(0.3)	(0.3)
Net loss	23.4	19.1	15.3
Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs	(1.1)	(1.1)	(1.1)
Net loss	$ 0.0	$ 0.0	$ (0.3)