Common Equity - Schedule of Earnings Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Net Income	$ 102.3	$ 18.6	$ 88.4	$ 38.3	$ 120.9	$ 126.7
Basic average common shares outstanding	200.8		200.3		200.6	200.3
Contingently issuable shares (performance and restricted stock units)	0.6		0.5		0.4	0.5
Diluted average common shares outstanding	201.4		200.8		201.0	200.8
Basic earnings per average common share	$ 0.51		$ 0.44		$ 0.6	$ 0.63
Diluted earnings per average common share	$ 0.51		$ 0.44		$ 0.6	$ 0.63
Anti-dilutive shares excluded from earnings per share calculation	0.0		0.0		0.0	0.0
Retained Earnings [Member]
Net Income	$ 102.3	$ 18.6	$ 88.4	$ 38.3	$ 120.9	$ 126.7