Exit Activities (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended		9 Months Ended		27 Months Ended
	Jul. 31, 2024	Apr. 30, 2024	Dec. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024
Appliance Service Plan Business
Restructuring Cost and Reserve [Line Items]
Proceeds from sale of ASP business		$ 124.0				$ 124.0	$ 0.0
Gain on disposition of assets		$ 110.0
Gain sharing with customers, percentage of gain			50.00%
Sharing period of gains			5 years
Gain on sale utilized as offset	$ 27.5
Amount credited to customers	$ 82.5
Amount credited to customers, term	3 years
Regulatory liability				$ 110.0		110.0		$ 110.0
Retention Benefits
Restructuring Cost and Reserve [Line Items]
Cost deferred				$ 3.0	$ 4.0	$ 6.0	$ 14.0
Retention Benefits | D.E. Karn Generating Complex and J.H. Campbell Generating Units | Retention Incentive Program
Restructuring Cost and Reserve [Line Items]
Regulatory asset collection period				3 years		3 years		3 years
Retention Benefits | J.H. Campbell Generating Units
Restructuring Cost and Reserve [Line Items]
Expected cost				$ 50.0		$ 50.0		$ 50.0
Retention Benefits | J.H. Campbell Generating Units | Retention Incentive Program
Restructuring Cost and Reserve [Line Items]
Cost deferred								$ 41.0