Income Taxes (Summary of Tax Loss and Tax Credit Carryforwards) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Tax Credit Carryforward [Line Items]
Deferred tax asset on tax carryforwards	$ 46.1	$ 48.4
Valuation allowance on tax carryforwards	(43.6)	$ (46.4)
Total
Tax Credit Carryforward [Line Items]
Deferred tax asset on tax carryforwards	46.1
Valuation allowance on tax carryforwards	(43.6)
Net deferred tax asset on tax carryforwards	2.5
U.S. Federal Tax Credits
Tax Credit Carryforward [Line Items]
2025-2029	0.0
After 2029	9.9
Indefinite	0.0
Total tax carryforwards	9.9
Deferred tax asset on tax carryforwards	9.9
Valuation allowance on tax carryforwards	(9.9)
Net deferred tax asset on tax carryforwards	0.0
U.S. Federal Tax Losses
Tax Credit Carryforward [Line Items]
2025-2029	0.0
After 2029	0.8
Indefinite	0.0
Total tax carryforwards	0.8
Deferred tax asset on tax carryforwards	0.2
Valuation allowance on tax carryforwards	(0.1)
Net deferred tax asset on tax carryforwards	0.1
U.S. State Tax Credits
Tax Credit Carryforward [Line Items]
2025-2029	1.1
After 2029	0.6
Indefinite	0.2
Total tax carryforwards	1.9
Deferred tax asset on tax carryforwards	1.5
Valuation allowance on tax carryforwards	(0.7)
Net deferred tax asset on tax carryforwards	0.8
U.S. State Tax Losses
Tax Credit Carryforward [Line Items]
2025-2029	113.2
After 2029	415.8
Indefinite	4.5
Total tax carryforwards	533.5
Deferred tax asset on tax carryforwards	29.4
Valuation allowance on tax carryforwards	(28.8)
Net deferred tax asset on tax carryforwards	0.6
Non- U.S. Tax Losses
Tax Credit Carryforward [Line Items]
2025-2029	0.3
After 2029	0.3
Indefinite	17.6
Total tax carryforwards	18.2
Deferred tax asset on tax carryforwards	4.3
Valuation allowance on tax carryforwards	(4.1)
Net deferred tax asset on tax carryforwards	0.2
Non US Tax Credits
Tax Credit Carryforward [Line Items]
2025-2029	0.0
After 2029	0.0
Indefinite	0.0
Total tax carryforwards	0.0
Deferred tax asset on tax carryforwards	0.8
Valuation allowance on tax carryforwards	0.0
Net deferred tax asset on tax carryforwards	$ 0.8