Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	$ 5	$ 8
Total contributions expected in current year	7
Total contributions to the plans during the period	2
Pension Benefits | Operation and maintenance expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	10
Pension Benefits | Other, net
Defined Benefit Plan Disclosure [Line Items]
Interest cost	15	15
Expected return on plan assets	(25)	(26)
Amortization of net loss	7	9
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	0	1
Total contributions expected in current year	8
Total contributions to the plans during the period	2
Other Postretirement Benefits Plan | Operation and maintenance expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Other Postretirement Benefits Plan | Other, net
Defined Benefit Plan Disclosure [Line Items]
Interest cost	2	2
Expected return on plan assets	(1)	(1)
Amortization of prior service cost (credit)	(1)	(1)
Amortization of net loss	(1)	0
Houston Electric | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total contributions expected in current year	0
Total contributions to the plans during the period	0
Houston Electric | Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	(2)	(1)
Total contributions expected in current year	1
Total contributions to the plans during the period	0
Houston Electric | Other Postretirement Benefits Plan | Operation and maintenance expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Houston Electric | Other Postretirement Benefits Plan | Other, net
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1
Expected return on plan assets	(1)	(1)
Amortization of prior service cost (credit)	(1)	(1)
Amortization of net loss	(1)	0
CERC Corp | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total contributions expected in current year	0
Total contributions to the plans during the period	0
CERC Corp | Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	1	1
Total contributions expected in current year	3
Total contributions to the plans during the period	0
CERC Corp | Other Postretirement Benefits Plan | Operation and maintenance expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
CERC Corp | Other Postretirement Benefits Plan | Other, net
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1
Expected return on plan assets	0	0
Amortization of prior service cost (credit)	0	0
Amortization of net loss	$ 0	$ 0