Leases (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) MW	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) MW	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) MW
Lease, Cost [Abstract]
Operating lease cost	$ 2	$ 2	$ 4	$ 6
Short-term lease cost	39	54	123	89
Variable lease cost	0	0	0	0
Total lease cost	41	56	127	95
Operating Leases, Lease Income [Abstract]
Operating lease income	1	1	4	4
Variable lease income	0	0	1	1
Total lease income	1	1	5	5
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets	15		15		$ 22
Finance ROU assets	367		367		179
Total leased assets	382		382		201
Current operating lease liability	5		5		6
Non-current operating lease liability	10		10		17
Total leased liabilities	$ 15		$ 15		$ 23
Weighted-average remaining lease term (in years) - operating leases	5 years		5 years		6 years 2 months 12 days
Weighted-average discount rate - operating leases (as a percent)	3.16%		3.16%		3.10%
Weighted-average remaining lease term (in years) - finance leases	6 years 9 months 18 days		6 years 9 months 18 days		7 years 6 months
Weighted-average discount rate - finance leases (as a percent)	2.73%		2.73%		2.21%
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 2022	$ 2		$ 2
2023	5		5
2024	4		4
2025	2		2
2026	2		2
2027 and beyond	2		2
Total lease payments	17		17
Less: Interest	2		2
Present value of lease liabilities	15		15		$ 23
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Finance lease, not yet commenced, amount	$ 271		$ 271
Lease not yet commenced, amount of megawatts | MW	220		220
Remainder of 2022	$ 1		$ 1
2023	7		7
2024	7		7
2025	7		7
2026	7		7
2027	7		7
2028 and beyond	160		160
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	1	2	4	5
Financing cash flows from finance leases included in the measurement of lease liabilities	47	0	218	0
Houston Electric
Lease Disclosure [Line Items]
Expenses associated with short-term lease	$ 90		$ 90		$ 20
Additional MW of mobile generation | MW	32		160
Cash payment	$ 47		$ 218
Number of megawatts of mobile generation | MW	505		505
Number of megawatts of mobile generation, amount delivered | MW	285		285		125
Expenses associated with long term lease	$ 41		$ 41		$ 1
Lease, Cost [Abstract]
Operating lease cost	0	0	0	0
Short-term lease cost	39	54	122	89
Variable lease cost	0	0	0	0
Total lease cost	39	54	122	89
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	0		0		1
Finance ROU assets	367		367		179
Total leased assets	367		367		180
Current operating lease liability	0		0		1
Non-current operating lease liability	0		0		0
Total leased liabilities	$ 0		$ 0		$ 1
Weighted-average remaining lease term (in years) - operating leases	5 years 4 months 24 days		5 years 4 months 24 days		4 years 1 month 6 days
Weighted-average discount rate - operating leases (as a percent)	3.50%		3.50%		2.86%
Weighted-average remaining lease term (in years) - finance leases	6 years 9 months 18 days		6 years 9 months 18 days		7 years 6 months
Weighted-average discount rate - finance leases (as a percent)	2.73%		2.73%		2.21%
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2022	$ 0		$ 0
2023	0		0
2024	0		0
2025	0		0
2026	0		0
2027 and beyond	0		0
Total lease payments	0		0
Less: Interest	0		0
Present value of lease liabilities	0		0		$ 1
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2022	0		0
2023	1		1
2024	1		1
2025	1		1
2026	0		0
2027	0		0
2028 and beyond	0		0
Total lease payments to be received	3		3
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	0	0	0	0
Financing cash flows from finance leases included in the measurement of lease liabilities	47	0	218	0
CERC
Lease, Cost [Abstract]
Operating lease cost	0	1	1	3
Short-term lease cost	1	0	1	0
Variable lease cost	0	0	0	0
Total lease cost	1	1	2	3
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	6		6		12
Finance ROU assets	0		0		0
Total leased assets	6		6		12
Current operating lease liability	2		2		2
Non-current operating lease liability	4		4		11
Total leased liabilities	$ 6		$ 6		$ 13
Weighted-average remaining lease term (in years) - operating leases	4 years 1 month 6 days		4 years 1 month 6 days		6 years 6 months
Weighted-average discount rate - operating leases (as a percent)	3.55%		3.55%		3.20%
Weighted-average discount rate - finance leases (as a percent)	0.00%		0.00%		0.00%
Operating Lease Liabilities, Payments Due [Abstract]
Remainder of 2022	$ 1		$ 1
2023	2		2
2024	2		2
2025	1		1
2026	1		1
2027 and beyond	0		0
Total lease payments	7		7
Less: Interest	1		1
Present value of lease liabilities	6		6		$ 13
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2022	1		1
2023	4		4
2024	4		4
2025	4		4
2026	4		4
2027	4		4
2028 and beyond	156		156
Total lease payments to be received	177		177
Other Information Related to Leases [Abstract]
Operating cash flows from operating leases included in the measurement of lease liabilities	0	1	1	3
Financing cash flows from finance leases included in the measurement of lease liabilities	$ 0	$ 0	$ 0	$ 0