Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (54.0)		$ (54.0)		$ (59.5)
Other Comprehensive Income (Loss), Net of Tax	1.8	$ 1.3	5.5	$ 3.9
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(54.0)	(63.5)	(54.0)	(63.5)	(59.5)	$ (67.3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			5.5	3.9
Other Comprehensive Income (Loss), Net of Tax			5.5	3.9
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Pension Plan [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(62.4)	(79.0)	(62.4)	(79.0)	(67.8)	(83.0)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			5.5	4.1
Other Comprehensive Income (Loss), Net of Tax			5.5	4.1
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Other Postretirement Benefits Plan [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 8.3	$ 15.5	8.3	15.5	$ 8.3	$ 15.7
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0.0	(0.2)
Other Comprehensive Income (Loss), Net of Tax			$ 0.0	$ (0.2)