Employee Benefit Plans (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		$ 11	$ 24	$ 36	$ 70
Total contributions expected in current year		84		84
Total contributions to the plans during the period		79		84
Increase in defined benefit plan, plan assets				$ 115
Percent increase (decrease) change in Defined Benefit Plan Assets				5.70%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		1	2	$ 3	6
Total contributions expected in current year		11		11
Total contributions to the plans during the period		2		8
Operation and maintenance expense [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[1]	10	10	32	30
Operation and maintenance expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[2]	1	2	2	3
Other, net [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[3]	18	25	56	73
Expected return on plan assets (2)	[3]	(28)	(27)	(85)	(79)
Amortization of prior service cost (2)	[3]	0	2	0	6
Amortization of net loss (2)	[3]	10	13	31	39
Settlement cost (2) (3)	[3],[4]	1	1	2	2
Curtailment gain (2) (4)	[3],[5]	0	0	0	(1)
Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[6]	2	4	8	12
Expected return on plan assets (2)	[6]	(1)	(3)	(4)	(6)
Amortization of prior service cost (2)	[6]	(1)	(1)	(3)	(3)
Houston Electric [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions expected in current year		0		0
Total contributions to the plans during the period		0		0
Houston Electric [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		(1)	(1)	(3)	(2)
Total contributions expected in current year		3		3
Total contributions to the plans during the period		1		3
Houston Electric [Member] | Operation and maintenance expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[2]	0	0	0	0
Houston Electric [Member] | Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[6]	1	1	4	5
Expected return on plan assets (2)	[6]	(1)	(1)	(3)	(3)
Amortization of prior service cost (2)	[6]	(1)	(1)	(4)	(4)
CERC Corp [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions expected in current year		0		0
Total contributions to the plans during the period		0		0
CERC Corp [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		1	2	3	4
Total contributions expected in current year		3		3
Total contributions to the plans during the period		1		2
CERC Corp [Member] | Operation and maintenance expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[2]	1	0	1	1
CERC Corp [Member] | Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[6]	0	2	2	4
Expected return on plan assets (2)	[6]	(1)	0	(1)	(1)
Amortization of prior service cost (2)	[6]	$ 1	$ 0	$ 1	$ 0

[1] Amounts presented in the table above are included in Operation and maintenance expense in CenterPoint Energy’s Condensed Statements of Consolidated Income, net of amounts capitalized and regulatory deferrals.

[2] Amounts presented in the tables above are included in Operation and maintenance expense in each of the Registrants’ respective Condensed Statements of Consolidated Income, net of amounts capitalized and regulatory deferrals.

[3] Amounts presented in the table above are included in Other income (expense), net in CenterPoint Energy’s Condensed Statements of Consolidated Income, net of regulatory deferrals.

[4] A one-time, non-cash settlement cost is required when the total lump sum distributions or other settlements of plan benefit obligations during a plan year exceed the service cost and interest cost components of the net periodic cost for that year. In each of the three and nine months ended September 30, 2020 and 2019, CenterPoint Energy recognized non-cash settlement costs due to lump sum settlement payments from Vectren pension plans.

[5] A curtailment gain or loss is required when the expected future services of a significant number of employees are reduced or eliminated for the accrual of benefits. In the nine months ended September 30, 2019, CenterPoint Energy recognized a pension curtailment gain related to Vectren employees whose employment was terminated after the Merger closed.

[6] Amounts presented in the tables above are included in Other income (expense), net in each of the Registrants’ respective Condensed Statements of Consolidated Income, net of regulatory deferrals.