Revenue - Summary of Disaggregates TEC Revenue by Major Source (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 505	$ 558	$ 1,378	$ 1,489
Total gas revenue	91	96	314	331
Total revenue	596	654	1,692	1,820
Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	303	325	762	792
Total gas revenue	29	30	113	116
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	128	160	374	421
Total gas revenue	30	32	99	109
Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	30	41	99	117
Total gas revenue	6	5	17	16
Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(8)	(31)	(13)	(21)
Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	52	63	156	180
Total gas revenue	26	29	85	90
Tampa Electric [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	506	559	1,381	1,492
Total gas revenue	0	0	0	0
Total revenue	506	559	1,381	1,492
Tampa Electric [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	303	325	762	792
Total gas revenue	0	0	0	0
Tampa Electric [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	128	160	374	421
Total gas revenue	0	0	0	0
Tampa Electric [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	30	41	99	117
Total gas revenue	0	0	0	0
Tampa Electric [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(8)	(31)	(13)	(21)
Tampa Electric [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	53	64	159	183
Total gas revenue	0	0	0	0
PGS [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	92	101	319	344
Total revenue	92	101	319	344
PGS [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	29	30	113	116
PGS [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	30	32	99	109
PGS [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	6	5	17	16
PGS [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
PGS [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	27	34	90	103
Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(1)	(1)	(3)	(3)
Total gas revenue	(1)	(5)	(5)	(13)
Total revenue	(2)	(6)	(8)	(16)
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)	(3)	(3)
Total gas revenue	$ (1)	$ (5)	$ (5)	$ (13)