Leases (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) MW	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) MW	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Lease Disclosure [Line Items]
Disallowance of regulatory asset	$ 53		$ 53
Lease, Cost [Abstract]
Operating lease cost	1	$ 2	4	$ 4
Short-term lease cost	15	39	28	123
Total lease cost	16	41	32	127
Operating Leases, Lease Income [Abstract]
Operating lease income	2	1	5	4
Variable lease income	0	0	1	1
Total lease income	2	1	6	5
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	15		15		$ 19
Finance ROU assets	550		550		621
Total leased assets	565		565		640
Current operating lease liability	4		4		5
Non-current operating lease liability	11		11		14
Total leased liabilities	$ 15		$ 15		$ 19
Weighted-average remaining lease term (in years) - operating leases	5 years 8 months 12 days		5 years 8 months 12 days		4 years 3 months 18 days
Weighted-average discount rate - operating leases	3.94%		3.94%		3.80%
Weighted-average remaining lease term (in years) - finance leases	5 years 9 months 18 days		5 years 9 months 18 days		6 years 6 months
Weighted-average discount rate - finance leases (as a percent)	3.60%		3.60%		3.60%
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other non-current assets		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		Property, Plant and Equipment, Net
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities		Other current liabilities		Other current liabilities
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other non-current liabilities		Other non-current liabilities		Other non-current liabilities
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2023	$ 2		$ 2
2024	3		3
2025	3		3
2026	3		3
2027	2		2
2028	2		2
2029 and beyond	1		1
Total lease payments	16		16
Less: Interest	1		1
Present value of lease liabilities	15		15		$ 19
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2023	2		2
2024	6		6
2025	8		8
2026	8		8
2027	7		7
2028	7		7
2029 and beyond	173		173
Total lease payments to be received	211		211
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	1	1	4	4
Financing cash flows from finance leases included in the measurement of lease liabilities	0	47	0	218
Houston Electric
Lease Disclosure [Line Items]
Expenses associated with short-term lease	$ 102		$ 102		103
Number of megawatts of mobile generation | MW	505		505
Escrow Deposit	$ 101		$ 101
Expenses associated with long term lease	$ 117		$ 117		60
Lease, Right To Terminate, Percentage Of Prepaid Lease Costs Refunded	75.00%		75.00%
Disallowance Of Reimbursement Clause Exercised			85.00%
Disallowance of regulatory asset	$ 53		$ 53
Lease, Cost [Abstract]
Operating lease cost	1	0	2	0
Short-term lease cost	14	39	27	122
Total lease cost	15	39	29	122
Operating Leases, Lease Income [Abstract]
Operating lease income	1	1	1	1
Variable lease income	0	0	0	0
Total lease income	1	1	1	1
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	6		6		6
Finance ROU assets	550		550		621
Total leased assets	556		556		627
Current operating lease liability	1		1		1
Non-current operating lease liability	5		5		5
Total leased liabilities	$ 6		$ 6		$ 6
Weighted-average remaining lease term (in years) - operating leases	4 years 1 month 6 days		4 years 1 month 6 days		4 years 9 months 18 days
Weighted-average discount rate - operating leases	4.09%		4.09%		4.01%
Weighted-average remaining lease term (in years) - finance leases	5 years 9 months 18 days		5 years 9 months 18 days		6 years 6 months
Weighted-average discount rate - finance leases (as a percent)	3.60%		3.60%		3.60%
Operating Lease Liabilities, Payments Due [Abstract]
Total lease payments	$ 7		$ 7
Less: Interest	1		1
Present value of lease liabilities	6		6		$ 6
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2023	0		0
2024	1		1
2025	1		1
2026	0		0
2027	0		0
2028	0		0
2029 and beyond	0		0
Total lease payments to be received	2		2
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	0	0	1	0
Financing cash flows from finance leases included in the measurement of lease liabilities	0	47	0	218
CERC
Lease, Cost [Abstract]
Operating lease cost	0	0	1	1
Short-term lease cost	0	1	0	1
Total lease cost	0	1	1	2
Operating Leases, Lease Income [Abstract]
Operating lease income	1	1	3	2
Variable lease income	0	0	0	0
Total lease income	1	1	3	2
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	4		4		5
Finance ROU assets	0		0		0
Total leased assets	4		4		5
Current operating lease liability	1		1		2
Non-current operating lease liability	3		3		4
Total leased liabilities	$ 4		$ 4		$ 6
Weighted-average remaining lease term (in years) - operating leases	3 years 3 months 18 days		3 years 3 months 18 days		3 years 10 months 24 days
Weighted-average discount rate - operating leases	3.60%		3.60%		3.58%
Weighted-average discount rate - finance leases (as a percent)	0.00%		0.00%		0.00%
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2023	$ 1		$ 1
2024	2		2
2025	1		1
2026	1		1
2027	0		0
2028	0		0
2029 and beyond	0		0
Total lease payments	5		5
Less: Interest	1		1
Present value of lease liabilities	4		4		$ 6
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2023	1		1
2024	5		5
2025	5		5
2026	5		5
2027	5		5
2028	5		5
2029 and beyond	170		170
Total lease payments to be received	196		196
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	0	0	1	1
Financing cash flows from finance leases included in the measurement of lease liabilities	$ 0	$ 0	$ 0	$ 0