Regulatory - Schedule of Regulatory Assets and Regulatory Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Regulatory assets:
Regulatory assets	$ 1,441	$ 988
Less: Current portion	343	161
Long-term regulatory assets	1,098	827
Regulatory liabilities:
Regulatory liabilities	904	795
Less: Current portion	146	94
Long-term regulatory liabilities	758	701
Regulatory Tax Asset [Member]
Regulatory assets:
Regulatory assets	117	112
Cost-Recovery Clauses [Member]
Regulatory assets:
Regulatory assets	20	94
Capital Cost Recovery for Early Retired Assets [Member]
Regulatory assets:
Regulatory assets	513	507
Capital cost recovery for retired Polk Unit 1 components
Regulatory assets:
Regulatory assets	142	0
Postretirement Benefits [Member]
Regulatory assets:
Regulatory assets	243	236
Storm Reserve [Member]
Regulatory assets:
Regulatory assets	377	7
Other [Member]
Regulatory assets:
Regulatory assets	29	32
Regulatory Tax Liability [Member] | Non-Current Liabilities [Member]
Regulatory liabilities:
Regulatory liabilities	456	477
Cost-recovery Clauses - Deferred Balances [Member]
Regulatory liabilities:
Regulatory liabilities	80	20
Accumulated Reserve - Cost of Removal [Member]
Regulatory liabilities:
Regulatory liabilities	304	271
Deferred production tax credits [Member]
Regulatory liabilities:
Regulatory liabilities	57	23
Other [Member]
Regulatory liabilities:
Regulatory liabilities	$ 7	$ 4