Common Equity - Schedule of Earnings Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Net Income	$ 38.3	$ 279.5
Basic average common shares outstanding	200.2	200.2
Contingently issuable shares (performance and restricted stock units)	0.6	0.4
Diluted average common shares outstanding	200.8	200.6
Basic earnings per average common share	$ 0.19	$ 1.40
Diluted earnings per average common share	$ 0.19	$ 1.39
Anti-dilutive shares excluded from earnings per share calculation	0.0	0.0
Retained Earnings [Member]
Net Income	$ 38.3	$ 279.5