Regulatory - Schedule of Regulatory Assets and Regulatory Liabilities (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Regulatory assets:
Regulatory assets	$ 1,414	$ 1,552
Less: Current portion	384	361
Long-term regulatory assets	1,030	1,191
Regulatory liabilities:
Regulatory liabilities	844	1,140
Less: Current portion	83	85
Long-term regulatory liabilities	761	1,055
Regulatory Tax Asset [Member]
Regulatory assets:
Regulatory assets	110	124
Cost-Recovery Clauses [Member]
Regulatory assets:
Regulatory assets	461	525
Capital Cost Recovery for Early Retired Assets [Member]
Regulatory assets:
Regulatory assets	493	497
Environmental Remediation [Member]
Regulatory assets:
Regulatory assets	0	20
Postretirement Benefits [Member]
Regulatory assets:
Regulatory assets	241	272
Asset Retirement Obligation [Member]
Regulatory assets:
Regulatory assets	10	13
Storm Reserve [Member]
Regulatory assets:
Regulatory assets	76	76
Other [Member]
Regulatory assets:
Regulatory assets	23	25
Regulatory Tax Liability [Member] | Non-Current Liabilities [Member]
Regulatory liabilities:
Regulatory liabilities	507	601
Cost-recovery Clauses - Deferred Balances [Member]
Regulatory liabilities:
Regulatory liabilities	22	30
Accumulated Reserve - Cost of Removal [Member]
Regulatory liabilities:
Regulatory liabilities	302	498
Other [Member]
Regulatory liabilities:
Regulatory liabilities	$ 13	$ 11