Revenue - Summary of Disaggregates TEC Revenue by Major Source (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 531	$ 453	$ 977	$ 873
Total gas revenue	123	96	276	223
Total revenue	654	549	1,253	1,096
Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	276	254	508	459
Total gas revenue	49	36	116	84
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	144	121	270	246
Total gas revenue	46	28	99	69
Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	41	32	78	69
Total gas revenue	6	5	12	11
Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	11	(3)	9	(5)
Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	59	49	112	104
Total gas revenue	22	27	49	59
Operating Segments [Member] | Tampa Electric [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	532	454	979	875
Total gas revenue	0	0	0	0
Total revenue	532	454	979	875
Operating Segments [Member] | Tampa Electric [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	276	254	508	459
Total gas revenue	0	0	0	0
Operating Segments [Member] | Tampa Electric [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	144	121	270	246
Total gas revenue	0	0	0	0
Operating Segments [Member] | Tampa Electric [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	41	32	78	69
Total gas revenue	0	0	0	0
Operating Segments [Member] | Tampa Electric [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	11	(3)	9	(5)
Operating Segments [Member] | Tampa Electric [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	60	50	114	106
Total gas revenue	0	0	0	0
Operating Segments [Member] | PGS [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	123	97	278	227
Total revenue	123	97	278	227
Operating Segments [Member] | PGS [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	49	36	116	84
Operating Segments [Member] | PGS [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	46	28	99	69
Operating Segments [Member] | PGS [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	6	5	12	11
Operating Segments [Member] | PGS [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Operating Segments [Member] | PGS [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	22	28	51	63
Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(1)	(1)	(2)	(2)
Total gas revenue	0	(1)	(2)	(4)
Total revenue	(1)	(2)	(4)	(6)
Eliminations [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	0	0	0	0
Eliminations [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	0	0	0	0
Eliminations [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	0	0	0	0
Eliminations [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Eliminations [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(1)	(1)	(2)	(2)
Total gas revenue	$ 0	$ (1)	$ (2)	$ (4)