Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 2,763	$ 2,547
Net income (loss)	531	280
Income from Discontinued Operations (net of tax expense of $—, $25, respectively)	0	83
Net income	531	363
Assets	35,202		$ 37,679
Assets Held for Sale	0		2,338
Continuing Operations
Segment Reporting Information [Line Items]
Assets	35,202		35,341
Houston Electric
Segment Reporting Information [Line Items]
Operating revenues	746	684
Net income	61	53
Assets	13,832		12,980
Houston Electric | Affiliates of NRG Energy, Inc.
Segment Reporting Information [Line Items]
Operating revenues	225	195
Houston Electric | Affiliates of Vistra Energy Corp.
Segment Reporting Information [Line Items]
Operating revenues	105	88
Electric | Affiliates of NRG Energy, Inc.
Segment Reporting Information [Line Items]
Operating revenues	225	195
Electric | Affiliates of Vistra Energy Corp.
Segment Reporting Information [Line Items]
Operating revenues	105	88
Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	1,824	1,663
Corporate and Other
Segment Reporting Information [Line Items]
Operating revenues	46	54
Corporate and Other | Pension and Other Postretirement Plans Costs
Segment Reporting Information [Line Items]
Regulatory assets	423		427
Operating Segments | Electric
Segment Reporting Information [Line Items]
Operating revenues	893	830
Net income (loss)	82	75
Assets	17,258		16,547
Operating Segments | Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	1,824	1,663
Net income (loss)	398	229
Assets	16,306		16,267
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Operating revenues	46	54
Net income (loss)	51	$ (24)
Assets	$ 1,638		$ 2,527