Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Benefits and compensation	$ 120	$ 141
Regulatory liabilities	396	435
Loss and credit carryforwards	76	103
Asset retirement obligations	130	152
Indexed debt securities derivative	36	47
Investment in unconsolidated affiliates	1	0
Other	50	52
Valuation allowance	(11)	(26)
Total deferred tax assets	798	904
Deferred tax liabilities:
Property, plant and equipment	2,912	2,790
Investment in unconsolidated affiliates	0	624
Regulatory assets	741	325
Investment in ZENS and equity securities related to ZENS	693	649
Investment in equity securities	195	0
Other	161	119
Total deferred tax liabilities	4,702	4,507
Net deferred tax liabilities	3,904	3,603
Houston Electric
Deferred tax assets:
Benefits and compensation	13	17
Regulatory liabilities	175	201
Asset retirement obligations	9	9
Other	10	9
Total deferred tax assets	207	236
Deferred tax liabilities:
Property, plant and equipment	1,215	1,159
Regulatory assets	114	118
Total deferred tax liabilities	1,329	1,277
Net deferred tax liabilities	1,122	1,041
CERC Corp
Deferred tax assets:
Benefits and compensation	25	28
Regulatory liabilities	139	147
Loss and credit carryforwards	571	143
Asset retirement obligations	118	140
Other	26	26
Valuation allowance	0	(15)
Total deferred tax assets	879	469
Deferred tax liabilities:
Property, plant and equipment	948	916
Regulatory assets	514	53
Other	97	84
Total deferred tax liabilities	1,559	1,053
Net deferred tax liabilities	$ 680	$ 584