Goodwill and Identifiable Intangible Assets and Liabilities - Schedule of Identifiable Intangible Assets and Liabilities Reported in the Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	$ 3,513	$ 2,937
Accumulated Amortization	2,641	2,414
Net	872	523
Total identifiable intangible assets	2,213	1,864
Total identifiable intangible liabilities	155	131
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 relationship
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	2,173	2,088
Accumulated Amortization	1,977	1,866
Net	196	222
Software and other technology-related assets
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	601	536
Accumulated Amortization	293	315
Net	308	221
Retail and wholesale contracts
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	503	233
Accumulated Amortization	353	217
Net	150	16
Long-term service agreements
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	18	18
Accumulated Amortization	5	5
Net	13	13
Total identifiable intangible liabilities	108	122
Other identifiable intangible assets
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	218	62
Accumulated Amortization	13	11
Net	205	51
Wholesale power and fuel purchase contracts
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Total identifiable intangible liabilities	$ 47	$ 9