Property, Plant, and Equipment - Narrative (Details) - USD ($)	5 Months Ended	7 Months Ended	12 Months Ended
	May 17, 2023	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2022	Jan. 01, 2025	Jan. 31, 2020
Property, Plant and Equipment [Line Items]
Aggregate fuel purchases	$ 14,000,000	$ 23,000,000	$ 35,000,000	$ 63,000,000
Discount rate			11.00%
Impairments (Note 10)	381,000,000	3,000,000	$ 1,000,000	$ 0
Nuclear fuel
Property, Plant and Equipment [Line Items]
Amortization of nuclear fuel intangible assets		53,000,000	33,000,000
Carrying Value		$ 56,000,000	$ 23,000,000
Susquehanna
Property, Plant and Equipment [Line Items]
Ownership interest		90.00%	90.00%
Conemaugh
Property, Plant and Equipment [Line Items]
Ownership interest			22.22%
Keystone
Property, Plant and Equipment [Line Items]
Ownership interest			12.34%
Talen Montana
Property, Plant and Equipment [Line Items]
Ownership interest			15.00%
Talen Montana | Colstrip Unit 3
Property, Plant and Equipment [Line Items]
Ownership interest			30.00%
Percentage of operating costs and expenditures			15.00%
Talen Montana | Colstrip Unit 4
Property, Plant and Equipment [Line Items]
Percentage of operating costs and expenditures			15.00%
Talen Montana | Colstrip Unit 1
Property, Plant and Equipment [Line Items]
Percentage of decommissioning and other related costs						50.00%
Talen Montana | Colstrip Unit 2
Property, Plant and Equipment [Line Items]
Percentage of decommissioning and other related costs						50.00%
Property, Plant, and Equipment, Brandon Shores
Property, Plant and Equipment [Line Items]
Impairments (Note 10)	$ 361,000,000
Property, Plant, and Equipment, Brandon Shores | Subsequent Event
Property, Plant and Equipment [Line Items]
Fixed-cost monthly payments					$ 12,083,333
Fixed-cost per day payments					312
Property, Plant, And Equipment, Wagner | Subsequent Event
Property, Plant and Equipment [Line Items]
Fixed-cost monthly payments					2,916,667
Fixed-cost per day payments					$ 137