Stock-Based Incentive Compensation Plans and Employee Benefit Plans - Pension and Postretirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Amounts Recognized in Balance Sheets
Other liabilities — benefit obligations	$ (511)	$ (680)
Changes in plan assets and benefit obligations recognized in other comprehensive income
Amortization of net loss	(7)	(7)
Amortization of prior service cost	(1)	0
Settlement (2)	(4)	0
Pension Plan
Components of net periodic costs [Abstract]
Service cost	38	43
Interest cost	59	75
Net periodic cost (credit)	$ 69	$ 49	$ 93
Assumptions used to determine net periodic benefit (income) cost
Expected return on plan assets (as a percent)	5.00%	5.00%
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year	$ 2,507	$ 2,453
Service cost	38	43
Interest cost	59	75
Benefits paid	(285)	(207)
Actuarial (gain) loss	(22)	143
Plan amendment	1	0
Benefit obligation, end of year	2,298	2,507	2,453
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year	2,135	2,005
Employer contributions	61	86
Benefits paid	(285)	(207)
Actual investment return	161	251
Fair value of plan assets, end of year	2,072	2,135	$ 2,005
Funded status, end of year	(226)	(372)
Amounts Recognized in Balance Sheets
Non-current assets	6	0
Current liabilities — other	(7)	(8)
Other liabilities — benefit obligations	(225)	(364)
Net liability, end of year	$ (226)	$ (372)
Discount rate (as a percent)	2.80%	2.45%
Rate of increase in compensation levels (as a percent)	4.95%	5.05%
Interest crediting rate (as a percent)	2.25%	2.25%
Pension benefits that have accumulated benefit obligations in excess of plan assets
Accumulated benefit obligation for all defined benefit pension plans	$ 2,278	$ 2,495
Amounts recognized in accumulated other comprehensive loss
Unrecognized actuarial loss (gain)	99	109
Unrecognized prior service cost	0	0
Net amount recognized in accumulated other comprehensive loss (gain)	99	109
Changes in plan assets and benefit obligations recognized in other comprehensive income
Net loss (gain)	1
Amortization of net loss	(7)
Amortization of prior service cost	0
Settlement (2)	(4)
Total recognized in comprehensive income	(10)
Total expense recognized in net periodic cost and other comprehensive income	59
Pension Plan | Qualified Plan
Change in plan assets [Rollforward]
Employer contributions	53
Pension benefits that have accumulated benefit obligations in excess of plan assets
Accumulated benefit obligation	2,216	2,427
Projected benefit obligation	2,237	2,440
Fair value of plan assets	2,072	2,135
Pension Plan | Nonqualified Plan
Change in plan assets [Rollforward]
Employer contributions	8
Pension benefits that have accumulated benefit obligations in excess of plan assets
Accumulated benefit obligation	62	68
Projected benefit obligation	62	68
Fair value of plan assets	$ 0	$ 0
Pension Plan | CenterPoint Energy
Assumptions used to determine net periodic benefit (income) cost
Discount rate (as a percent)	2.45%	3.20%	4.35%
Expected return on plan assets (as a percent)	5.00%	5.75%	6.00%
Rate of increase in compensation levels (as a percent)	5.05%	4.95%	4.60%
Other Postretirement Benefits Plan
Components of net periodic costs [Abstract]
Service cost	$ 2	$ 2	$ 3
Interest cost	9	11	15
Expected return on plan assets	(4)	(5)	(5)
Amortization of prior service cost	(4)	(4)	(5)
Net periodic cost (credit)	$ 3	$ 4	$ 8
Assumptions used to determine net periodic benefit (income) cost
Discount rate (as a percent)	2.50%	3.25%	3.20%
Expected return on plan assets (as a percent)	3.20%	3.95%	4.60%
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year	$ 366	$ 356
Service cost	2	2	$ 3
Interest cost	9	11	15
Participant contributions	7	6
Benefits paid	(21)	(22)
Early Retiree Reinsurance Program	20	0
Actuarial (gain) loss	(47)	13
Plan amendment	0	0
Benefit obligation, end of year	336	366	356
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year	134	128
Employer contributions	7	10
Participant contributions	7	6
Benefits paid	(21)	(22)
Actual investment return	5	12
Fair value of plan assets, end of year	132	134	128
Funded status, end of year	(204)	(232)
Amounts Recognized in Balance Sheets
Current liabilities — other	(7)	(9)
Other liabilities — benefit obligations	(197)	(223)
Net liability, end of year	$ (204)	$ (232)
Discount rate (as a percent)	2.85%	2.50%
Expected return on plan assets (as a percent)	3.22%	3.20%
Pension benefits that have accumulated benefit obligations in excess of plan assets
Prescription drug cost trend rate assumed for the next year - Pre-65	8.00%	7.50%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.50%	4.50%
Amounts recognized in accumulated other comprehensive loss
Unrecognized actuarial loss (gain)	$ (23)	$ (14)
Unrecognized prior service cost	13	7
Net amount recognized in accumulated other comprehensive loss (gain)	(10)	$ (7)
Changes in plan assets and benefit obligations recognized in other comprehensive income
Net loss (gain)	(2)
Amortization of net loss	0
Amortization of prior service cost	(1)
Settlement (2)	0
Total recognized in comprehensive income	(3)
Total expense recognized in net periodic cost and other comprehensive income	$ 0
Minimum | Other Postretirement Benefits Plan
Pension benefits that have accumulated benefit obligations in excess of plan assets
Health care cost trend rate assumed for the next year	6.00%	5.25%
Maximum | Other Postretirement Benefits Plan
Pension benefits that have accumulated benefit obligations in excess of plan assets
Health care cost trend rate assumed for the next year	18.71%	19.70%
Houston Electric
Amounts Recognized in Balance Sheets
Other liabilities — benefit obligations	$ (55)	$ (75)
Changes in plan assets and benefit obligations recognized in other comprehensive income
Amortization of net loss	0	0
Amortization of prior service cost	0	0
Settlement (2)	0	0
Houston Electric | Pension Plan | Qualified Plan
Change in plan assets [Rollforward]
Employer contributions	0
Houston Electric | Pension Plan | Nonqualified Plan
Change in plan assets [Rollforward]
Employer contributions	0
Houston Electric | Other Postretirement Benefits Plan
Components of net periodic costs [Abstract]
Service cost	0	0	1
Interest cost	4	5	7
Expected return on plan assets	(3)	(4)	(4)
Amortization of prior service cost	(5)	(5)	(6)
Net periodic cost (credit)	$ (4)	$ (4)	$ (2)
Assumptions used to determine net periodic benefit (income) cost
Discount rate (as a percent)	2.50%	3.25%	3.20%
Expected return on plan assets (as a percent)	3.30%	4.05%	4.70%
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year	$ 168	$ 162
Service cost	0	0	$ 1
Interest cost	4	5	7
Participant contributions	2	2
Benefits paid	(9)	(10)
Early Retiree Reinsurance Program	0	0
Actuarial (gain) loss	(22)	9
Plan amendment	5	0
Benefit obligation, end of year	148	168	162
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year	106	101
Employer contributions	1	3
Participant contributions	2	2
Benefits paid	(9)	(10)
Actual investment return	4	10
Fair value of plan assets, end of year	104	106	101
Funded status, end of year	(44)	(62)
Amounts Recognized in Balance Sheets
Current liabilities — other	0	0
Other liabilities — benefit obligations	(44)	(62)
Net liability, end of year	$ (44)	$ (62)
Discount rate (as a percent)	2.85%	2.50%
Expected return on plan assets (as a percent)	3.32%	3.30%
Pension benefits that have accumulated benefit obligations in excess of plan assets
Prescription drug cost trend rate assumed for the next year - Pre-65	8.00%	7.50%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.50%	4.50%
Houston Electric | Minimum | Other Postretirement Benefits Plan
Pension benefits that have accumulated benefit obligations in excess of plan assets
Health care cost trend rate assumed for the next year	6.00%	5.25%
Houston Electric | Maximum | Other Postretirement Benefits Plan
Pension benefits that have accumulated benefit obligations in excess of plan assets
Health care cost trend rate assumed for the next year	18.71%	19.70%
CERC Corp
Amounts Recognized in Balance Sheets
Other liabilities — benefit obligations	$ (81)	$ (83)
Changes in plan assets and benefit obligations recognized in other comprehensive income
Amortization of net loss	0	0
Amortization of prior service cost	(1)	(1)
Settlement (2)	0	0
CERC Corp | Pension Plan | Qualified Plan
Change in plan assets [Rollforward]
Employer contributions	0
CERC Corp | Pension Plan | Nonqualified Plan
Change in plan assets [Rollforward]
Employer contributions	0
CERC Corp | Other Postretirement Benefits Plan
Components of net periodic costs [Abstract]
Service cost	1	1	1
Interest cost	3	3	5
Expected return on plan assets	(1)	(1)	(1)
Amortization of prior service cost	1	1	1
Net periodic cost (credit)	$ 4	$ 4	$ 6
Assumptions used to determine net periodic benefit (income) cost
Discount rate (as a percent)	2.50%	3.25%	3.20%
Expected return on plan assets (as a percent)	2.85%	3.35%	4.15%
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year	$ 105	$ 102
Service cost	1	1	$ 1
Interest cost	3	3	5
Participant contributions	2	2
Benefits paid	(6)	(6)
Early Retiree Reinsurance Program	11	0
Actuarial (gain) loss	(11)	3
Plan amendment	0	0
Benefit obligation, end of year	105	105	102
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year	28	27
Employer contributions	3	3
Participant contributions	2	2
Benefits paid	(6)	(6)
Actual investment return	1	2
Fair value of plan assets, end of year	28	28	27
Funded status, end of year	(77)	(77)
Amounts Recognized in Balance Sheets
Current liabilities — other	(3)	(3)
Other liabilities — benefit obligations	(73)	(74)
Net liability, end of year	$ (76)	$ (77)
Discount rate (as a percent)	2.85%	2.50%
Expected return on plan assets (as a percent)	2.86%	2.85%
Pension benefits that have accumulated benefit obligations in excess of plan assets
Prescription drug cost trend rate assumed for the next year - Pre-65	8.00%	7.50%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.50%	4.50%
Amounts recognized in accumulated other comprehensive loss
Unrecognized actuarial loss (gain)	$ (18)	$ (12)
Unrecognized prior service cost	12	7
Net amount recognized in accumulated other comprehensive loss (gain)	(6)	$ (5)
Changes in plan assets and benefit obligations recognized in other comprehensive income
Net loss (gain)	0
Amortization of net loss	0
Amortization of prior service cost	(1)
Settlement (2)	0
Total recognized in comprehensive income	(1)
Total expense recognized in net periodic cost and other comprehensive income	$ 3
CERC Corp | Minimum | Other Postretirement Benefits Plan
Pension benefits that have accumulated benefit obligations in excess of plan assets
Health care cost trend rate assumed for the next year	6.00%	5.25%
CERC Corp | Maximum | Other Postretirement Benefits Plan
Pension benefits that have accumulated benefit obligations in excess of plan assets
Health care cost trend rate assumed for the next year	18.71%	19.70%
Operation And Maintenance Expense | Pension Plan
Components of net periodic costs [Abstract]
Service cost	$ 39	$ 43	40
Change in benefit obligation [Roll Forward]
Service cost	39	43	40
Other Nonoperating Income (Expense) | Pension Plan
Components of net periodic costs [Abstract]
Interest cost	59	75	96
Expected return on plan assets	(103)	(112)	(105)
Amortization of prior service cost	0	0	9
Amortization of net loss	36	41	52
Settlement cost	38	2	2
Curtailment gain	0	0	(1)
Change in benefit obligation [Roll Forward]
Interest cost	$ 59	$ 75	$ 96