Exit Activities - Narrative (Details) - Retention Benefits - USD ($) $ in Millions	3 Months Ended		9 Months Ended	42 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Cost deferred	$ 5	$ 1
D.E. Karn Generating Complex
Restructuring Cost and Reserve [Line Items]
Aggregate cost incurred						$ 31
Retention and severance costs				$ 16
D.E. Karn Generating Complex | Forecast
Restructuring Cost and Reserve [Line Items]
Expected cost					$ 2
D.E. Karn Generating Complex | Retention Incentive Program
Restructuring Cost and Reserve [Line Items]
Cost deferred				12
D.E. Karn Generating Complex | Property, Plant and Equipment
Restructuring Cost and Reserve [Line Items]
Costs incurred and capitalized				4
J.H. Campbell Generating Units
Restructuring Cost and Reserve [Line Items]
Expected cost	$ 50		$ 50	$ 50
J.H. Campbell Generating Units | Retention Incentive Program
Restructuring Cost and Reserve [Line Items]
Cost deferred			$ 24