Employee Benefit Plans (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		$ 24	$ 15	$ 46	$ 30
Total contributions expected in current year		94		94
Total contributions to the plans during the period		27		29
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		2	2	4	3
Total contributions expected in current year		20		20
Total contributions to the plans during the period		3		8
Operation and maintenance expense [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[1]	10	9	20	18
Operation and maintenance expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[2]	0	1	1	1
Other, net [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[3]	25	19	48	39
Expected return on plan assets (2)	[3]	(27)	(26)	(52)	(53)
Amortization of prior service cost (credit) (2)	[3]	2	2	4	4
Amortization of net loss (2)	[3]	13	11	26	22
Settlement cost (3)	[4]	1	0	1	0
Curtailment gain	[5]	0	0	1	0
Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[6]	4	4	8	7
Expected return on plan assets (2)	[6]	(1)	(2)	(3)	(3)
Amortization of prior service cost (credit) (2)	[6]	(1)	(1)	(2)	(2)
Houston Electric [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		(1)	(1)	(1)	(1)
Total contributions expected in current year		10		10
Total contributions to the plans during the period		2		5
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]	2	2	4	4
Expected return on plan assets (2)	[6]	(1)	(1)	(2)	(2)
Amortization of prior service cost (credit) (2)	[6]	(2)	(2)	(3)	(3)
CERC Corp [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (income)		1	1	2	2
Total contributions expected in current year		4		4
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	0
CERC Corp [Member] | Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[6]	1	1	2	2
Expected return on plan assets (2)	[6]	(1)	(1)	(1)	(1)
Amortization of prior service cost (credit) (2)	[6]	$ 0	$ 1	$ 0	$ 1

[1] Amounts presented in the table 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.

[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 each of the Registrants’ respective 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 June 2019, CenterPoint Energy recognized a non-cash settlement cost of $1 million 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 February 2019, CenterPoint Energy recognized a pension curtailment gain of $1 million 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.