Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 1,944	$ 1,742	$ 4,707	$ 4,289
Net income (loss)	190	200	721	480
Net income from discontinued operations	0	51	0	134
Net income	190	251	721	614
Total Assets	36,216		36,216		$ 37,679
Assets Held for Sale	0		0		2,338
Continuing Operations
Segment Reporting Information [Line Items]
Total Assets	36,216		36,216		35,341
Houston Electric
Segment Reporting Information [Line Items]
Operating revenues	881	786	1,627	1,470
Net income	147	103	208	156
Total Assets	14,306		14,306		12,980
Houston Electric | Affiliates of NRG Energy, Inc.
Segment Reporting Information [Line Items]
Operating revenues	245	192	470	387
Houston Electric | Affiliates of Vistra Energy Corp.
Segment Reporting Information [Line Items]
Operating revenues	114	87	219	175
Electric | Affiliates of NRG Energy, Inc.
Segment Reporting Information [Line Items]
Operating revenues	245	192	470	387
Electric | Affiliates of Vistra Energy Corp.
Segment Reporting Information [Line Items]
Operating revenues	114	87	219	175
Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	818	740	2,642	2,403
Corporate and Other
Segment Reporting Information [Line Items]
Operating revenues	73	65	119	119
Corporate and Other | Pension and Other Postretirement Plans Costs
Segment Reporting Information [Line Items]
Regulatory assets	436		436		427
Operating Segments | Electric
Segment Reporting Information [Line Items]
Operating revenues	1,053	937	1,946	1,767
Net income (loss)	173	125	255	200
Total Assets	17,769		17,769		16,548
Operating Segments | Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	818	740	2,642	2,403
Net income (loss)	28	74	426	303
Total Assets	16,237		16,237		16,270
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Operating revenues	73	65	119	119
Net income (loss)	(11)	$ 1	40	$ (23)
Total Assets	$ 2,210		$ 2,210		$ 2,523