Income Taxes (Taxes by Jurisdiction) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current Income Tax Expense (Benefit)	$ 1.6	$ 1.0	$ 0.4
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	1.5	(14.6)	39.5
Provision (benefit) for income taxes	0.1	15.6	(39.1)
Domestic Tax Authority [Member]
Current Income Tax Expense (Benefit)	0.0	0.0	0.0
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	0.7	(14.9)	40.7
State and Local Jurisdiction [Member]
Current Income Tax Expense (Benefit)	1.6	1.0	0.4
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	0.8	0.3	(1.2)
Foreign Tax Authority [Member]
Current Income Tax Expense (Benefit)	0.0	0.0	0.0
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 0.0	$ 0.0	$ 0.0