Significant Accounting Policies - Summary of Assets and Liabilities of PGS in TEC's Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, plant and equipment
Utility plant	$ 14,433	$ 13,655
Accumulated depreciation	3,348	3,443
Total property, plant and equipment, net	11,103	10,228
Current assets
Cash and cash equivalents	4	5
Receivables, less allowance for credit losses of $1 at December 31, 2022	220	286
Inventories, at average cost
Regulatory assets	343	161
Prepayments and other current assets	32	32
Total current assets	848	720
Other assets
Regulatory assets	1,098	827
Deferred charges and other assets	58	56
Total other assets	1,156	883
Total assets	13,107	11,831	$ 13,803
Capitalization
Common stock	5,105	4,505
Accumulated other comprehensive loss	(1)	(1)
Retained earnings	218	219
Total capital	5,322	4,723	5,420	$ 4,792
Long-term debt	3,935	3,933
Total capital	9,257	8,656
Current liabilities
Long-term debt due within one year	0	300
Notes payable	636	209
Accounts payable	666	354
Customer deposits	126	121
Regulatory liabilities	146	94
Accrued interest	31	28
Accrued taxes	12	14
Other	58	43
Total current liabilities	1,693	1,173
Other liabilities
Deferred income taxes	976	880
Regulatory liabilities	758	701
Deferred credits and other liabilities	199	184
Total Other liabilities	2,157	2,002
Total liabilities and capital	13,107	11,831
PGS [Member]
Property, plant and equipment
Utility plant			2,938
Accumulated depreciation			(687)
Total property, plant and equipment, net			2,251
Current assets
Cash and cash equivalents			4
Receivables, less allowance for credit losses of $1 at December 31, 2022			62
Due from affiliates			4
Inventories, at average cost
Regulatory assets			53
Prepayments and other current assets			4
Total current assets			88
Other assets
Regulatory assets			9
Deferred charges and other assets			79
Total other assets			132
Total assets			2,471
Capitalization
Common stock			871
Retained earnings			121
Total capital			992
Long-term debt			564
Total capital			1,556
Current liabilities
Notes payable			166
Accounts payable			78
Due to affiliates			27
Customer deposits			30
Regulatory liabilities			277
Accrued interest			4
Accrued taxes			5
Other			4
Total current liabilities			325
Other liabilities
Deferred income taxes			238
Regulatory liabilities			11
Deferred credits and other liabilities			75
Total Other liabilities			590
Total liabilities and capital			2,471
Fuel [Member]
Inventories, at average cost
Utility inventories	45	36
Materials and Supplies [Member]
Inventories, at average cost
Utility inventories	$ 191	$ 181
Materials and Supplies [Member] | PGS [Member]
Inventories, at average cost
Utility inventories			$ 5