Non-operating Income (Expense) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Nonoperating Income (Expense) [Abstract]
Interest Expense	$ (11.5)	$ (12.7)	$ (23.7)	$ (24.6)
Interest Costs Capitalized	0.0	2.0	0.0	5.4
Amortization of Debt Issuance Costs	(0.5)	(0.4)	(1.1)	(0.9)
Interest Income, Other	0.0	0.3	0.0	0.7
Interest Expense, Net	(12.0)	(10.9)	(24.9)	(19.4)
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	(2.0)	(1.5)	(3.8)	(2.8)
Nonoperating Income (Expense)	(14.9)	(12.4)	(29.6)	(22.2)
Term Loan [Member]
Nonoperating Income (Expense) [Abstract]
Write off of Deferred Debt Issuance Cost	1.0	0.0	1.0	0.0
Write off of Deferred Debt Issuance Cost	$ 1.0	$ 0.0	$ 1.0	$ 0.0