Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Total revenues	$ 795	$ 912	$ 2,024	$ 2,424
Total interest charges	61	44	180	117
Net income	170	169	381	432
Total assets	12,638		12,638		$ 13,803
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	795	912	2,024	2,424
Related Party [Member]
Segment Reporting Information [Line Items]
Total interest charges	3	0	8	0
Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Total revenues	0
Intracompany Sales [Member] | Related Party [Member]
Segment Reporting Information [Line Items]
Total revenues		0	0	0
Eliminations/Reclassifications [Member]
Segment Reporting Information [Line Items]
Total revenues		(2)		(6)
Total interest charges		0		0
Net income		0		0
Total assets	(648)		(648)		(732)
Eliminations/Reclassifications [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues		0		0
Eliminations/Reclassifications [Member] | Intracompany Sales [Member] | Related Party [Member]
Segment Reporting Information [Line Items]
Total revenues		(2)		(6)
Tampa Electric [Member]
Segment Reporting Information [Line Items]
Total revenues	795	753	2,024	1,926
Tampa Electric [Member] | Intracompany Sales [Member] | Related Party [Member]
Segment Reporting Information [Line Items]
Total revenues	0
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	795	753	2,024	1,926
Total interest charges	61	37	180	99
Net income	170	153	381	367
Total assets	13,286		13,286		12,064
Tampa Electric [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	$ 795	752	2,024	1,923
Tampa Electric [Member] | Operating Segments [Member] | Intracompany Sales [Member] | Related Party [Member]
Segment Reporting Information [Line Items]
Total revenues		1	$ 0	3
PGS [Member]
Segment Reporting Information [Line Items]
Total revenues		161		504
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues		161		504
Total interest charges		7		18
Net income		16		65
Total assets					$ 2,471
PGS [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues		160		501
PGS [Member] | Operating Segments [Member] | Intracompany Sales [Member] | Related Party [Member]
Segment Reporting Information [Line Items]
Total revenues		$ 1		$ 3