Revenue Recognition and Allowance for Credit Losses - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts	$ 1,872	$ 1,959	$ 4,633	$ 4,747
Other	3	(15)	21	(40)
Total	1,875	1,944	4,654	4,707
Lease income	2	3	4	4
Houston Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts	918	892	1,721	1,648
Other	(9)	(11)	(20)	(21)
Total	909	881	1,701	1,627
CERC
Disaggregation of Revenue [Line Items]
Revenue from contracts	737	805	2,437	2,590
Other	8	(9)	25	(30)
Total	745	796	2,462	2,560
Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts	1,040	1,060	1,998	1,958
Other	(3)	(7)	(9)	(12)
Total	1,037	1,053	1,989	1,946
Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts	759	827	2,511	2,672
Other	5	(9)	28	(30)
Total	764	818	2,539	2,642
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts	73	72	124	117
Other	1	1	2	2
Total	$ 74	$ 73	$ 126	$ 119