Income Taxes - Schedule of Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income tax reconciliation [Abstract]
Income before income taxes	$ 778	$ 563	$ 545
Increase (decrease) in tax expense resulting from:
State law change, net of federal income tax	(39)
State valuation allowance, net of federal income tax		(4)
Excess deferred income tax amortization	(76)	(55)
Total income tax expense (benefit)	$ 110	$ 80	$ 30
Houston Electric
Other Tax Carryforward [Line Items]
Effective tax rate (as a percent)	17.00%	14.00%	18.00%
Income tax reconciliation [Abstract]
Income before income taxes	$ 457	$ 387	$ 436
Federal statutory income tax rate (as a percent)	21.00%	21.00%	21.00%
Expected federal income tax expense	$ 96	$ 81	$ 92
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	18	15	16
Excess deferred income tax amortization	(41)	(42)	(21)
Other, net	3	(1)	(7)
Total	(20)	(28)	(12)
Total income tax expense (benefit)	$ 76	$ 53	$ 80
Effective tax rate (as a percent)	17.00%	14.00%	18.00%
CERC Corp
Income tax reconciliation [Abstract]
Income before income taxes	$ 305	$ 244	$ 186
Increase (decrease) in tax expense resulting from:
State valuation allowance, net of federal income tax		(4)
Excess deferred income tax amortization	(16)	(18)
Total income tax expense (benefit)	$ 51	97	$ (3)
CERC Corp | State and Local Jurisdiction
Increase (decrease) in tax expense resulting from:
Reduction in income taxes due to tax reform		$ 4
Continuing Operations
Other Tax Carryforward [Line Items]
Effective tax rate (as a percent)	14.00%	14.00%	6.00%
Income tax reconciliation [Abstract]
Income before income taxes	$ 778	$ 563	$ 545
Federal statutory income tax rate (as a percent)	21.00%	21.00%	21.00%
Expected federal income tax expense	$ 163	$ 118	$ 114
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	63	40	27
State law change, net of federal income tax	23	0	33
State valuation allowance, net of federal income tax	15	(1)	4
Excess deferred income tax amortization	(75)	(76)	(55)
Goodwill impairment	0	39	0
Net operating loss carryback	0	(37)	0
Other, net	(3)	(5)	(19)
Total	(53)	(38)	(84)
Total income tax expense (benefit)	$ 110	$ 80	$ 30
Effective tax rate (as a percent)	14.00%	14.00%	6.00%
Operating loss carryback, CARES Act	$ 37
Continuing Operations | CERC Corp
Other Tax Carryforward [Line Items]
Effective tax rate (as a percent)	17.00%	40.00%	(2.00%)
Income tax reconciliation [Abstract]
Income before income taxes	$ 305	$ 244	$ 186
Federal statutory income tax rate (as a percent)	21.00%	21.00%	21.00%
Expected federal income tax expense	$ 64	$ 51	$ 39
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	33	55	(15)
State law change, net of federal income tax	15	0	4
State valuation allowance, net of federal income tax	15	(1)	4
Excess deferred income tax amortization	16	16	18
Other, net	0	6	(1)
Total	(13)	46	(42)
Total income tax expense (benefit)	$ 51	$ 97	$ (3)
Effective tax rate (as a percent)	17.00%	40.00%	(2.00%)
Discontinued Operations
Other Tax Carryforward [Line Items]
Effective tax rate (as a percent)	20.00%	21.00%	28.00%
Income tax reconciliation [Abstract]
Income before income taxes	$ 1,019	$ (1,589)	$ 384
Federal statutory income tax rate (as a percent)	21.00%	21.00%	21.00%
Expected federal income tax expense	$ 214	$ (334)	$ 81
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	14	(60)	9
State law change, net of federal income tax	27	0	(12)
Goodwill impairment	0	25	8
Tax impact of sale of Energy Services and Infrastructure Services Disposal Groups	0	30	0
Other, net	0	6	(2)
Total	(13)	1	27
Total income tax expense (benefit)	$ 201	$ (333)	$ 108
Effective tax rate (as a percent)	20.00%	21.00%	28.00%
Discontinued Operations | CERC Corp
Other Tax Carryforward [Line Items]
Effective tax rate (as a percent)	0.00%	3.00%	43.00%
Income tax reconciliation [Abstract]
Income (loss) before income taxes	$ 0	$ (68)	$ 40
Federal statutory income tax rate (as a percent)	0.00%	21.00%	21.00%
Expected federal income tax expense	$ 0	$ (14)	$ 8
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	0	(2)	3
Goodwill impairment	0	10	8
Other, net	0	4	(2)
Total	0	12	9
Total income tax expense (benefit)	$ 0	$ (2)	$ 17
Effective tax rate (as a percent)	0.00%	3.00%	43.00%