Financing (Total Indebtedness to Capitalization) (Details) $ in Millions	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Disclosure [Abstract]
Short-term borrowings	$ 210.0	$ 4.6
Long-term debt	540.6	640.3
Total debt	750.6
Equity	1,064.9	$ 964.0	$ 783.8	$ 763.8
Capitalization	$ 1,815.5
Total indebtedness to capitalization	0.413