Accounting Policies - Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Gross Carrying Value, Non-amortizable	$ 38.2	$ 38.2
Gross Carrying Value, Amortizable	100.3	100.3
Total Intangible Assets	138.5	138.5
Accumulated Amortization, Intangible Assets	84.3	78.2
Amortization Expense, Intangible Assets	$ 6.1	$ 6.5	$ 6.5