Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Total Operating revenues	$ 11,122	$ 6,788
Total Purchased power and fuel expenses	(6,352)	(4,384)
Total RNF	4,770	2,404
Operating Segments
Segment Reporting Information [Line Items]
Total Operating revenues	8,400	5,585
Total Purchased power and fuel expenses	(4,723)	(3,117)
Total RNF	3,677	2,468
Operating Segments \| Mid-Atlantic
Segment Reporting Information [Line Items]
Total Operating revenues	1,847	1,665
Total Purchased power and fuel expenses	(1,035)	(856)
Total RNF	812	809
Operating Segments \| Midwest
Segment Reporting Information [Line Items]
Total Operating revenues	1,732	1,404
Total Purchased power and fuel expenses	(878)	(554)
Total RNF	854	850
Operating Segments \| New York
Segment Reporting Information [Line Items]
Total Operating revenues	569	562
Total Purchased power and fuel expenses	(160)	(161)
Total RNF	409	401
Operating Segments \| ERCOT
Segment Reporting Information [Line Items]
Total Operating revenues	370	398
Total Purchased power and fuel expenses	(161)	(184)
Total RNF	209	214
Operating Segments \| Other Power Regions
Segment Reporting Information [Line Items]
Total Operating revenues	1,487	1,556
Total Purchased power and fuel expenses	(1,220)	(1,362)
Total RNF	267	194
Operating Segments \| Calpine
Segment Reporting Information [Line Items]
Total Operating revenues	2,395
Total Purchased power and fuel expenses	(1,269)
Total RNF	1,126
Segment Reconciling Items
Segment Reporting Information [Line Items]
Total Operating revenues	2,722	1,203
Total Purchased power and fuel expenses	(1,629)	(1,267)
Total RNF	1,093	(64)
Unrealized mark-to-market gains (losses)	254	34
Segment Reconciling Items \| Product and Service, Other
Segment Reporting Information [Line Items]
Unrealized mark-to-market gains (losses)	$ 1,315	$ (287)