Significant Accounting Policies - Summary of Assets and Liabilities of PGS in TEC's Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 13, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, plant and equipment
Utility plant	$ 15,474		$ 14,189
Accumulated depreciation	3,845		3,601
Total property, plant and equipment, net	11,644		10,602
Current assets
Cash and cash equivalents	14		18
Receivables, less allowance for credit losses of $1 at December 31, 2022	295		254
Due from affiliates	22		8
Inventories, at average cost
Regulatory assets	361		136
Prepayments and other current assets	35		22
Total current assets	909		579
Other assets
Regulatory assets	1,191		866
Deferred charges and other assets	59		149
Total other assets	1,250		1,015
Total assets	13,803	$ 13,803	12,196	$ 11,048
Capitalization
Common stock	5,075		4,470
Accumulated other comprehensive loss	(1)		(1)
Retained earnings	346		323
Total capital	5,420		4,792	$ 4,216	$ 3,695
Long-term debt	3,734		3,136
Total capital	9,154		7,928
Current liabilities
Long-term debt due within one year	0		250
Notes payable	1,019		745
Accounts payable	472		390
Due to affiliates	226		44
Customer deposits	145		132
Regulatory liabilities	85		78
Accrued interest	30		18
Accrued taxes	15		19
Other	45		51
Total current liabilities	2,037		1,727
Other liabilities
Deferred income taxes	1,045		858
Regulatory liabilities	1,055		1,092
Deferred credits and other liabilities	269		342
Total Other liabilities	2,612		2,541
Total liabilities and capital	13,803		12,196
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	23		20
Materials and Supplies [Member]
Inventories, at average cost
Utility inventories	159		$ 121
Materials and Supplies [Member] | PGS [Member]
Inventories, at average cost
Utility inventories	$ 5