Reportable Segments - Revenues From Major External Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenues	$ 8,696	$ 9,321	$ 8,352
Houston Electric
Segment Reporting Information [Line Items]
Revenues	3,677	3,412	3,134
Affiliates of NRG | Houston Electric
Segment Reporting Information [Line Items]
Revenues	1,106	1,046	905
Affiliates of Vistra Energy Corp. | Houston Electric
Segment Reporting Information [Line Items]
Revenues	$ 539	$ 489	$ 410