Reportable Segments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) state	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Revenues	$ 2,547	$ 2,167
Equity in earnings from investment in Enable	108	(1,475)
Net income (loss)	363	(1,053)
Income (Loss) from Discontinued Operations	0	(146)
Net income (loss)	363	(1,199)
Assets	35,906		$ 33,471
Enable Midstream Partners [Member]
Segment Reporting Information [Line Items]
Equity in earnings from investment in Enable	108	(1,475)
Impairment of CenterPoint Energy's equity method investment in Enable	0	1,541
Houston Electric [Member]
Segment Reporting Information [Line Items]
Revenues	684	634
Net income (loss)	53	33
Assets	12,185		11,316
Houston Electric [Member] | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues	195	156
Houston Electric [Member] | Affiliates of Vistra Energy Corp. [Member]
Segment Reporting Information [Line Items]
Revenues	88	81
CERC Corp [Member]
Segment Reporting Information [Line Items]
Revenues	1,177	1,011
Income (Loss) from Discontinued Operations	0	(64)
Net income (loss)	151	67
Assets	10,356		8,308
Electric | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues	195	156
Electric | Affiliates of Vistra Energy Corp. [Member]
Segment Reporting Information [Line Items]
Revenues	$ 88	81
Natural Gas [Member]
Segment Reporting Information [Line Items]
Number of States in which the Entity Performs Gas Delivery Services | state	48
Revenues	$ 1,663	1,321
Natural Gas [Member] | CERC Corp [Member]
Segment Reporting Information [Line Items]
Number of States in which the Entity Performs Gas Delivery Services | state	48
Revenues	$ 1,177	1,011
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	54	79
Corporate and Other, Net | Pension and Other Postretirement Plans Costs
Segment Reporting Information [Line Items]
Regulatory Assets	533		540
Operating Segments [Member] | Electric
Segment Reporting Information [Line Items]
Revenues	830	767
Equity in earnings from investment in Enable	0	0
Net income (loss)	75	(134)
Assets	15,410		14,493
Operating Segments [Member] | Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	1,663	1,321
Equity in earnings from investment in Enable	0	0
Net income (loss)	229	201
Assets	17,208		14,976
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Equity in earnings from investment in Enable	108	(1,475)
Net income (loss)	71	(1,127)
Assets	994		913
Corporate, Non-Segment | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	54	79
Equity in earnings from investment in Enable	0	0
Net income (loss)	(12)	$ 7
Corporate, Non-Segment | Corporate and Other, Net
Segment Reporting Information [Line Items]
Assets	$ 2,294		$ 3,089