Revenue Recognition - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,990	$ 1,849	$ 6,899	$ 6,349
Other	(2)	7	(45)	32
Revenues from external customers	1,988	1,856	6,852	6,381
Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers			(2)
Houston Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,139	1,065	3,045	3,024
Other	(7)	(7)	(21)	(21)
Revenues from external customers	1,132	1,058	3,024	3,003
CERC
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	602	593	3,157	2,760
Other	5	7	(31)	31
Revenues from external customers	607	600	3,126	2,791
Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,372	1,245	3,639	3,504
Other	(7)	(2)	(17)	(5)
Revenues from external customers	1,365	1,243	3,622	3,499
Electric \| Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers			0
Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	617	603	3,256	2,842
Other	5	8	(30)	34
Revenues from external customers	622	611	3,224	2,876
Natural Gas \| Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers			(2)
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	4	3
Other	0	1	2	3
Revenues from external customers	$ 1	$ 2	6	$ 6
Corporate and Other \| Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers			$ 0