Goodwill and Identifiable Intangible Assets and Liabilities - Schedule of Identifiable Intangible Assets and Liabilities Reported in the Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	$ 3,675	$ 3,513
Accumulated Amortization	2,764	2,641
Net	911	872
Total identifiable intangible assets	2,252	2,213
Total identifiable intangible liabilities	144	155
Retail trade names (not subject to amortization)
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Retail trade names (not subject to amortization)	1,341	1,341
Retail customer relationships
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	2,173	2,173
Accumulated Amortization	2,022	1,977
Net	151	196
Software and other technology-related assets
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	640	601
Accumulated Amortization	329	293
Net	311	308
Retail and wholesale contracts
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	503	503
Accumulated Amortization	392	353
Net	111	150
Long-term service agreements
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	18	18
Accumulated Amortization	6	5
Net	12	13
Total identifiable intangible liabilities	101	108
Other identifiable intangible assets
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	341	218
Accumulated Amortization	15	13
Net	326	205
Wholesale power and fuel purchase contracts
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Total identifiable intangible liabilities	$ 43	$ 47