Leases (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($) MW	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) MW	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Lease, Cost [Abstract]
Operating lease cost	$ 1	$ 1	$ 2	$ 3
Short-term lease cost	6	13	8	13
Total lease cost	7	14	10	16
Operating Leases, Lease Income [Abstract]
Operating lease income	1	1	3	3
Variable lease income	1	0	1	1
Total lease income	2	1	4	4
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	17		17		$ 13
Finance ROU assets	478		478		526
Total leased assets	495		495		539
Current operating lease liability	3		3		3
Non-current operating lease liability	14		14		10
Total leased liabilities	$ 17		$ 17		$ 13
Weighted-average remaining lease term (in years) - operating leases	11 years 7 months 6 days		11 years 7 months 6 days		4 years 8 months 12 days
Weighted-average discount rate - operating leases	4.49%		4.49%		4.13%
Weighted-average remaining lease term (in years) - finance leases	5 years		5 years		5 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 2024	$ 2		$ 2
2025	4		4
2026	4		4
2027	2		2
2028	1		1
2029	10		10
2030 and beyond	1		1
Total lease payments	24		24
Less: Interest	7		7
Present value of lease liabilities	17		17		$ 13
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2024	3		3
2025	6		6
2026	7		7
2027	7		7
2028	7		7
2029	7		7
2030 and beyond	158		158
Total lease payments to be received	195		195
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities			2	3
Houston Electric
Lease Disclosure [Line Items]
Expenses associated with short-term lease	$ 95		$ 95		100
Number of megawatts of mobile generation | MW	505		505
Escrow deposit	$ 88		$ 88
Expenses associated with long term lease	$ 139		$ 139		124
Right to terminate, lease costs refunded (as a percent)	75.00%		75.00%
Lease, Cost [Abstract]
Operating lease cost	$ 1	0	$ 2	1
Short-term lease cost	5	14	7	13
Total lease cost	6	14	9	14
Operating Leases, Lease Income [Abstract]
Operating lease income	0	0	0	0
Variable lease income	0	0	0	0
Total lease income	0	0	0	0
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	6		6		6
Finance ROU assets	478		478		526
Total leased assets	484		484		532
Current operating lease liability	1		1		1
Non-current operating lease liability	4		4		5
Total leased liabilities	$ 5		$ 5		$ 6
Weighted-average remaining lease term (in years) - operating leases	3 years 4 months 24 days		3 years 4 months 24 days		3 years 10 months 24 days
Weighted-average discount rate - operating leases	4.11%		4.11%		4.09%
Weighted-average remaining lease term (in years) - finance leases	5 years		5 years		5 years 6 months
Weighted-average discount rate - finance leases (as a percent)	3.60%		3.60%		3.60%
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2024	$ 1		$ 1
2025	2		2
2026	1		1
2027	1		1
2028	0		0
2029	0		0
2030 and beyond	0		0
Total lease payments	5		5
Less: Interest	0		0
Present value of lease liabilities	5		5		$ 6
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2024	0		0
2025	1		1
2026	0		0
2027	0		0
2028	0		0
2029	0		0
2030 and beyond	0		0
Total lease payments to be received	1		1
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities			1	1
CERC
Lease, Cost [Abstract]
Operating lease cost	1	1	1	1
Short-term lease cost	0	0	0	0
Total lease cost	1	1	1	1
Operating Leases, Lease Income [Abstract]
Operating lease income	1	1	2	2
Variable lease income	0	0	0	0
Total lease income	1	$ 1	2	2
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	4		4		4
Finance ROU assets	0		0		0
Total leased assets	4		4		4
Current operating lease liability	1		1		1
Non-current operating lease liability	3		3		3
Total leased liabilities	$ 4		$ 4		$ 4
Weighted-average remaining lease term (in years) - operating leases	3 years 4 months 24 days		3 years 4 months 24 days		3 years 1 month 6 days
Weighted-average discount rate - operating leases	3.95%		3.95%		3.60%
Weighted-average discount rate - finance leases (as a percent)	0.00%		0.00%		0.00%
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2024	$ 1		$ 1
2025	2		2
2026	1		1
2027	0		0
2028	0		0
2029	0		0
2030 and beyond	0		0
Total lease payments	4		4
Less: Interest	0		0
Present value of lease liabilities	4		4		$ 4
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2024	2		2
2025	4		4
2026	5		5
2027	5		5
2028	5		5
2029	6		6
2030 and beyond	156		156
Total lease payments to be received	$ 183		183
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities			$ 1	$ 1