Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 14,761	$ 13,804	$ 15,631
Operating revenues	17,224	14,779	13,728
Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	24,730	21,355	18,482
Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Operating revenues	(7,506)	(6,576)	(4,754)
Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	11,659	9,316	9,110
Operating revenues	12,797	10,572	9,455
Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	821	1,695	1,973
Operating revenues	5,394	3,979	3,878
Texas | Operating Segments | Operating revenues
Disaggregation of Revenue [Line Items]
Unrealized gain (loss) on derivatives affiliated	74	(48)	(780)
East | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,823	2,193	3,319
Operating revenues	5,661	5,890	4,429
East | Operating Segments | Operating revenues
Disaggregation of Revenue [Line Items]
Unrealized gain (loss) on derivatives affiliated	(195)	814	(45)
West | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	458	600	618
Operating revenues	877	914	336
West | Operating Segments | Operating revenues
Disaggregation of Revenue [Line Items]
Unrealized gain (loss) on derivatives affiliated	4	(6)	2
Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	611
Operating revenues	1	0	384
Asset Closure | Operating Segments | Operating revenues
Disaggregation of Revenue [Line Items]
Unrealized gain (loss) on derivatives affiliated			4
Retail energy charge in ERCOT
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	8,064	7,674	6,971
Retail energy charge in ERCOT | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in ERCOT | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	8,064	7,674	6,971
Retail energy charge in ERCOT | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in ERCOT | East | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in ERCOT | West | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in ERCOT | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in Northeast/Midwest
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3,595	1,642	2,139
Retail energy charge in Northeast/Midwest | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in Northeast/Midwest | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3,595	1,642	2,139
Retail energy charge in Northeast/Midwest | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in Northeast/Midwest | East | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in Northeast/Midwest | West | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Retail energy charge in Northeast/Midwest | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Wholesale generation revenue from ISO/RTO
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,978	2,909	4,293
Wholesale generation revenue from ISO/RTO | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Wholesale generation revenue from ISO/RTO | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Wholesale generation revenue from ISO/RTO | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	399	1,190	1,277
Wholesale generation revenue from ISO/RTO | East | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,351	1,298	1,987
Wholesale generation revenue from ISO/RTO | West | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	228	421	467
Wholesale generation revenue from ISO/RTO | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	562
Capacity revenue from ISO/RTO
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	74	98	103
Capacity revenue from ISO/RTO | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Capacity revenue from ISO/RTO | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Capacity revenue from ISO/RTO | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Capacity revenue from ISO/RTO | East | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	74	98	76
Net capacity sold		233	361
Net capacity purchased		135	285
Capacity revenue from ISO/RTO | East | Operating Segments | Operating revenues
Disaggregation of Revenue [Line Items]
Net capacity sold	126
Net capacity purchased	52
Capacity revenue from ISO/RTO | East | Operating Segments | Fuel, purchased power costs, and delivery fees/Depreciation and amortization
Disaggregation of Revenue [Line Items]
Net capacity sold	116	73	167
Net capacity purchased	139	82	212
Capacity revenue from ISO/RTO | West | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Capacity revenue from ISO/RTO | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	27
Net capacity sold			27
Revenue from other wholesale contracts
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,050	1,481	2,125
Revenue from other wholesale contracts | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Revenue from other wholesale contracts | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Revenue from other wholesale contracts | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	422	505	696
Revenue from other wholesale contracts | East | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	398	797	1,256
Revenue from other wholesale contracts | West | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	230	179	151
Revenue from other wholesale contracts | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	22
Total other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	2,463	975	(1,903)
Total other revenues | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Operating revenues	(7,506)	(6,576)	(4,754)
Total other revenues | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	1,138	1,256	345
Total other revenues | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	4,573	2,284	1,905
Total other revenues | East | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	3,838	3,697	1,110
Total other revenues | West | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	419	314	(282)
Total other revenues | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	1	0	(227)
Transferable PTC revenues
Disaggregation of Revenue [Line Items]
Operating revenues	556	10
Transferable PTC revenues | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
Transferable PTC revenues | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
Transferable PTC revenues | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	292	10
Transferable PTC revenues | East | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	264	0
Transferable PTC revenues | West | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
Transferable PTC revenues | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
Hedging revenues — realized
Disaggregation of Revenue [Line Items]
Operating revenues	895	252	264
Hedging revenues — realized | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	1
Hedging revenues — realized | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	1,241	1,063	875
Hedging revenues — realized | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	(453)	(885)	(67)
Hedging revenues — realized | East | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	31	43	(247)
Hedging revenues — realized | West | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	84	67	35
Hedging revenues — realized | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	(8)	(36)	(333)
Hedging revenue — unrealized
Disaggregation of Revenue [Line Items]
Operating revenues	1,013	714	(2,163)
Hedging revenue — unrealized | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Hedging revenue — unrealized | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	(168)	191	(532)
Hedging revenue — unrealized | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	700	(714)	(637)
Hedging revenue — unrealized | East | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	143	958	(770)
Hedging revenue — unrealized | West | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	329	243	(326)
Hedging revenue — unrealized | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	9	36	102
Intangible amortization and other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	(1)	(1)	(4)
Intangible amortization and other revenues | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Operating revenues	2	2	0
Intangible amortization and other revenues | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	1	2	2
Intangible amortization and other revenues | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Intangible amortization and other revenues | East | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	(4)	(5)	(6)
Intangible amortization and other revenues | West | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Intangible amortization and other revenues | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Intersegment sales
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Intersegment sales | Eliminations / Corporate and Other
Disaggregation of Revenue [Line Items]
Operating revenues	(7,508)	(6,578)	(4,755)
Intersegment sales | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	64	0	0
Intersegment sales | Texas | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	4,034	3,873	2,609
Intersegment sales | East | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	3,404	2,701	2,133
Intersegment sales | West | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	6	4	9
Intersegment sales | Asset Closure | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	$ 0	$ 0	$ 4