Regulatory - Schedule of Regulatory Assets and Regulatory Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Regulatory assets:
Regulatory assets	$ 1,367	$ 1,002
Less: Current portion	524	136
Long-term regulatory assets	843	866
Regulatory liabilities:
Regulatory liabilities	1,149	1,170
Less: Current portion	73	78
Long-term regulatory liabilities	1,076	1,092
Regulatory Tax Asset [Member]
Regulatory assets:
Regulatory assets	131	117
Cost-Recovery Clauses Regulatory Assets [Member]
Regulatory assets:
Regulatory assets	441	89
Capital Cost Recovery for Early Retired Assets [Member]
Regulatory assets:
Regulatory assets	502	518
Environmental Remediation [Member]
Regulatory assets:
Regulatory assets	22	22
Postretirement Benefits [Member]
Regulatory assets:
Regulatory assets	215	230
Asset Retirement Obligation [Member]
Regulatory assets:
Regulatory assets	12	11
Storm Reserve [Member]
Regulatory assets:
Regulatory assets	21	0
Other [Member]
Regulatory assets:
Regulatory assets	23	15
Regulatory Tax Liability [Member] | Non-Current Liabilities [Member]
Regulatory liabilities:
Regulatory liabilities	625	638
Cost-Recovery Clauses - Deferred Balances Regulatory Liabilities [Member]
Regulatory liabilities:
Regulatory liabilities	43	16
Accumulated Reserve - Cost of Removal [Member]
Regulatory liabilities:
Regulatory liabilities	476	468
Storm Reserve [Member]
Regulatory liabilities:
Regulatory liabilities	0	46
Other [Member]
Regulatory liabilities:
Regulatory liabilities	$ 5	$ 2