Significant Accounting Policies - Summary of Assets and Liabilities of PGS in TEC's Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, plant and equipment
Utility plant	$ 13,655	$ 15,474
Accumulated depreciation	3,443	3,845
Total property, plant and equipment, net	10,228	11,644
Current assets
Cash and cash equivalents	5	14
Receivables, less allowance for credit losses of $1 at December 31, 2022	286	295
Inventories, at average cost
Regulatory assets	161	361
Prepayments and other current assets	32	35
Total current assets	720	909
Other assets
Regulatory assets	827	1,191
Deferred charges and other assets	56	59
Total other assets	883	1,250
Total assets	11,831	13,803	$ 12,196
Capitalization
Common stock	4,505	5,075
Accumulated other comprehensive loss	(1)	(1)
Retained earnings	219	346
Total capital	4,723	5,420	$ 4,792	$ 4,216
Long-term debt	3,933	3,734
Total capital	8,656	9,154
Current liabilities
Long-term debt due within one year	300	0
Notes payable	209	1,019
Accounts payable	354	472
Customer deposits	121	145
Regulatory liabilities	94	85
Accrued interest	28	30
Accrued taxes	14	15
Other	43	45
Total current liabilities	1,173	2,037
Other liabilities
Deferred income taxes	880	1,045
Regulatory liabilities	701	1,055
Deferred credits and other liabilities	184	269
Total Other liabilities	2,002	2,612
Total liabilities and capital	11,831	13,803
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		1,556
Long-term debt		564
Total capital		992
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	36	23
Materials and Supplies [Member]
Inventories, at average cost
Utility inventories	$ 181	159
Materials and Supplies [Member] | PGS [Member]
Inventories, at average cost
Utility inventories		$ 5