Leases (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) MW	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Lease Disclosure [Line Items]
Disallowance of regulatory asset	$ 53
Lease, Cost [Abstract]
Operating lease cost	2	$ 2
Short-term lease cost	0	46
Variable lease cost	0	(1)
Total lease cost	2	47
Operating Leases, Lease Income [Abstract]
Operating lease income	2	1
Total lease income	2	1
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	19		$ 19
Finance ROU assets	597		621
Total leased assets	616		640
Current operating lease liability	5		5
Non-current operating lease liability	13		14
Total leased liabilities	$ 18		$ 19
Weighted-average remaining lease term (in years) - operating leases	4 years 2 months 12 days		4 years 3 months 18 days
Weighted-average discount rate - operating leases (as a percent)	3.86%		3.80%
Weighted-average remaining lease term (in years) - finance leases	6 years 3 months 18 days		6 years 6 months
Weighted-average discount rate - finance leases (as a percent)	3.60%		3.60%
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other non-current assets		Other non-current assets
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, Plant and Equipment, Net		Property, Plant and Equipment, Net
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities		Other current liabilities
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other non-current liabilities		Other non-current liabilities
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2023	$ 5
2024	5
2025	4
2026	4
2027	2
2028 and beyond	0
Total lease payments	20
Less: Interest	2
Present value of lease liabilities	18		$ 19
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2023	4
2024	7
2025	7
2026	7
2027	7
2028	6
2029 and beyond	154
Total lease payments to be received	192
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	2	2
Financing cash flows from finance leases included in the measurement of lease liabilities	0	171
Houston Electric
Lease Disclosure [Line Items]
Expenses associated with short-term lease	$ 105		103
Number of megawatts of mobile generation | MW	505
Escrow Deposit	$ 113
Expenses associated with long term lease	$ 90		60
Lease, Right To Terminate, Percentage Of Prepaid Lease Costs Refunded	75.00%
Disallowance Of Reimbursement Clause Exercised	85.00%
Disallowance of regulatory asset	$ 53
Lease, Cost [Abstract]
Operating lease cost	1	0
Short-term lease cost	(1)	46
Variable lease cost	0	(1)
Total lease cost	0	45
Operating Leases, Lease Income [Abstract]
Operating lease income	0	0
Total lease income	0	0
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	8		6
Finance ROU assets	597		621
Total leased assets	605		627
Current operating lease liability	1		1
Non-current operating lease liability	6		5
Total leased liabilities	$ 7		$ 6
Weighted-average remaining lease term (in years) - operating leases	4 years 7 months 6 days		4 years 9 months 18 days
Weighted-average discount rate - operating leases (as a percent)	4.07%		4.01%
Weighted-average remaining lease term (in years) - finance leases	6 years 3 months 18 days		6 years 6 months
Weighted-average discount rate - finance leases (as a percent)	3.60%		3.60%
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2023	$ 1
2024	2
2025	2
2026	2
2027	1
2028 and beyond	0
Total lease payments	8
Less: Interest	1
Present value of lease liabilities	7		$ 6
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2023	0
2024	1
2025	1
2026	0
2027	0
2028	0
2029 and beyond	0
Total lease payments to be received	2
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	0	0
Financing cash flows from finance leases included in the measurement of lease liabilities	0	171
CERC
Lease, Cost [Abstract]
Operating lease cost	0	1
Short-term lease cost	0	0
Variable lease cost	0	0
Total lease cost	0	1
Operating Leases, Lease Income [Abstract]
Operating lease income	1	1
Total lease income	1	1
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	5		5
Finance ROU assets	0		0
Total leased assets	5		5
Current operating lease liability	1		2
Non-current operating lease liability	4		4
Total leased liabilities	$ 5		$ 6
Weighted-average remaining lease term (in years) - operating leases	3 years 8 months 12 days		3 years 10 months 24 days
Weighted-average discount rate - operating leases (as a percent)	3.58%		3.58%
Weighted-average discount rate - finance leases (as a percent)	0.00%		0.00%
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2023	$ 2
2024	2
2025	1
2026	1
2027	0
2028 and beyond	0
Total lease payments	6
Less: Interest	1
Present value of lease liabilities	5		$ 6
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2023	3
2024	4
2025	4
2026	4
2027	4
2028	5
2029 and beyond	151
Total lease payments to be received	175
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	0	1
Financing cash flows from finance leases included in the measurement of lease liabilities	$ 0	$ 0