Goodwill and Identifiable Intangible Assets and Liabilities - Schedule of Identifiable Intangible Assets and Liabilities Reported in the Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	$ 3,683	$ 3,513
Accumulated Amortization	2,703	2,641
Net	980	872
Total identifiable intangible assets	2,321	2,213
Total identifiable intangible liabilities	149	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	1,999	1,977
Net	174	196
Software and other technology-related assets
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	616	601
Accumulated Amortization	312	293
Net	304	308
Retail and wholesale contracts
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	503	503
Accumulated Amortization	373	353
Net	130	150
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	104	108
Other identifiable intangible assets
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Gross Carrying Amount	373	218
Accumulated Amortization	14	13
Net	359	205
Wholesale power and fuel purchase contracts
Finite-Lived and Indefinite-Lived Intangible [Line Items]
Total identifiable intangible liabilities	$ 45	$ 47