Common Equity - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	$ 39.3	$ 9.7	$ 34.8
Related tax benefit	10.8	2.7	9.6
Stock options
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	4.9	5.3	6.5
Restricted stock
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	7.6	6.6	7.0
Performance units
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	$ 26.8	$ (2.2)	$ 21.3