Revenue Recognition and Allowance for Credit Losses - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts	$ 1,906	$ 1,740	$ 6,653	$ 5,996
Other	(3)	9	(43)	42
Total	1,903	1,749	6,610	6,038
Lease income	1	2	5	6
Houston Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts	949	880	2,597	2,358
Other	(14)	(6)	(35)	(14)
Total	935	874	2,562	2,344
CERC
Disaggregation of Revenue [Line Items]
Revenue from contracts	667	602	3,257	2,893
Other	5	7	(25)	32
Total	672	609	3,232	2,925
Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts	1,155	1,056	3,113	2,822
Other	(9)	0	(21)	1
Total	1,146	1,056	3,092	2,823
Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts	686	611	3,358	2,984
Other	6	8	(24)	38
Total	692	619	3,334	3,022
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts	65	73	182	190
Other	0	1	2	3
Total	$ 65	$ 74	$ 184	$ 193