Employee Benefit Plans (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost		$ 22	$ 15
Total contributions expected in current year		94
Total contributions to the plans during the period		2
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost		2	1
Total contributions expected in current year		20
Total contributions to the plans during the period		5
Operation and maintenance expense [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[1]	10	9
Operation and maintenance expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[1]	1	0
Other, net [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[2]	23	20
Expected return on plan assets (2)	[2]	(25)	(27)
Amortization of prior service cost (credit) (2)	[2]	2	2
Amortization of net loss (2)	[2]	13	11
Curtailment gain	[3]	(1)	0
Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[2]	4	3
Expected return on plan assets (2)	[2]	(2)	(1)
Amortization of prior service cost (credit) (2)	[2]	(1)	(1)
Houston Electric [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost		0	0
Total contributions expected in current year		10
Total contributions to the plans during the period		3
Houston Electric [Member] | Operation and maintenance expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[1]	0	0
Houston Electric [Member] | Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[2]	2	2
Expected return on plan assets (2)	[2]	(1)	(1)
Amortization of prior service cost (credit) (2)	[2]	(1)	(1)
CERC Corp [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost		1	1
Total contributions expected in current year		4
Total contributions to the plans during the period		1
CERC Corp [Member] | Operation and maintenance expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (1)	[1]	0	0
CERC Corp [Member] | Other, net [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost (2)	[2]	1	1
Expected return on plan assets (2)	[2]	0	0
Amortization of prior service cost (credit) (2)	[2]	$ 0	$ 0

[1] 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.

[2] 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.

[3] 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 of 2019, CenterPoint Energy recognized a pension curtailment gain of $1 million related to Vectren employees whose employment was terminated after the Merger closed.