Investments and Fair Value Measurements (Cost and Fair Value of Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale	$ 2.4	$ 2.2
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Current	3.6	4.0
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Noncurrent	0.0	0.0
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss	3.6	4.0
Debt Securities, Held-to-maturity, Maturity [Abstract]
Held-to-maturity securities, due within one year, fair value	3.6	4.0
Held-to-maturity securities, due within one year, fair value	0.0	0.0
Held-to-maturity securities, current	$ 3.6	$ 4.0