Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Total revenues	$ 691	$ 599
Total interest charges	35	33
Net income	118	92
Total assets	12,448		$ 12,196
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	691	599
Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	0	0
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(2)	(3)
Total interest charges	0	0
Net income	0	0
Total assets	(688)		(663)
Eliminations [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	0	0
Eliminations [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	(2)	(3)
Tampa Electric [Member]
Segment Reporting Information [Line Items]
Total revenues	510	447
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	510	447
Total interest charges	30	28
Net income	88	65
Total assets	10,873		10,650
Tampa Electric [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	509	446
Tampa Electric [Member] | Operating Segments [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	1	1
PGS [Member]
Segment Reporting Information [Line Items]
Total revenues	183	155
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	183	155
Total interest charges	5	5
Net income	30	27
Total assets	2,263		$ 2,209
PGS [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	182	153
PGS [Member] | Operating Segments [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	$ 1	$ 2