Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenue from contracts with customers	$ 20,841	$ 21,571	$ 17,254
Revenue not from contracts	4,077	2,869	2,395
Revenues	24,918	24,440	19,649
Electricity
Segment Reporting Information [Line Items]
Revenues	19,014	19,684	16,290
Mid-Atlantic | Electricity
Segment Reporting Information [Line Items]
Revenues	5,138	5,164	4,584
Midwest | Electricity
Segment Reporting Information [Line Items]
Revenues	4,658	4,650	4,060
New York | Electricity
Segment Reporting Information [Line Items]
Revenues	2,021	1,595	1,575
ERCOT | Electricity
Segment Reporting Information [Line Items]
Revenues	1,346	1,543	1,181
Other Power Regions  | Electricity
Segment Reporting Information [Line Items]
Revenues	5,851	6,732	4,890
Operating Segments | Electricity
Segment Reporting Information [Line Items]
Revenue from contracts with customers	18,397	18,421	15,112
Revenue not from contracts	617	1,263	1,178
Revenues	19,014	19,684	16,290
Operating Segments | Mid-Atlantic | Electricity
Segment Reporting Information [Line Items]
Revenue from contracts with customers	5,453	5,264	4,381
Revenue not from contracts	(265)	(105)	183
Revenues	5,188	5,159	4,564
Operating Segments | Midwest | Electricity
Segment Reporting Information [Line Items]
Revenue from contracts with customers	4,846	5,164	4,265
Revenue not from contracts	(191)	(507)	(205)
Revenues	4,655	4,657	4,060
Operating Segments | New York | Electricity
Segment Reporting Information [Line Items]
Revenue from contracts with customers	1,910	2,004	1,633
Revenue not from contracts	56	(408)	(57)
Revenues	1,966	1,596	1,576
Operating Segments | ERCOT | Electricity
Segment Reporting Information [Line Items]
Revenue from contracts with customers	1,232	954	896
Revenue not from contracts	109	602	276
Revenues	1,341	1,556	1,172
Operating Segments | Other Power Regions  | Electricity
Segment Reporting Information [Line Items]
Revenue from contracts with customers	4,956	5,035	3,937
Revenue not from contracts	908	1,681	981
Revenues	5,864	6,716	4,918
Intersegment Revenues | Mid-Atlantic | Electricity
Segment Reporting Information [Line Items]
Revenues	(50)	5	20
Intersegment Revenues | Midwest | Electricity
Segment Reporting Information [Line Items]
Revenues	3	(7)	0
Intersegment Revenues | New York | Electricity
Segment Reporting Information [Line Items]
Revenues	55	(1)	(1)
Intersegment Revenues | ERCOT | Electricity
Segment Reporting Information [Line Items]
Revenues	5	(13)	9
Intersegment Revenues | Other Power Regions  | Electricity
Segment Reporting Information [Line Items]
Revenues	(13)	16	(28)
Segment Reconciling Items
Segment Reporting Information [Line Items]
Unrealized mark-to-market gains (losses)	(972)	(1,013)	565
Segment Reconciling Items | Natural Gas
Segment Reporting Information [Line Items]
Revenue from contracts with customers	1,859	2,559	1,777
Revenue not from contracts	1,866	2,408	1,602
Revenues	3,725	4,967	3,379
Segment Reconciling Items | Product and Service, Other
Segment Reporting Information [Line Items]
Revenue from contracts with customers	585	591	365
Revenue not from contracts	1,594	(802)	(385)
Revenues	2,179	(211)	(20)
Unrealized mark-to-market gains (losses)	$ 1,399	$ (1,188)	$ (633)