Revenue - Summary of Disaggregates TEC Revenue by Major Source (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 1,845	$ 1,961	$ 2,063
Total gas revenue	427	443	461
Total revenue	2,272	2,404	2,524
Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	1,018	1,046	1,067
Total gas revenue	158	154	157
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	506	562	582
Total gas revenue	135	146	151
Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	133	156	161
Total gas revenue	23	21	21
Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(25)	(49)	(2)
Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	213	246	255
Total gas revenue	111	122	132
Tampa Electric [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	1,849	1,965	2,066
Total gas revenue	0	0	0
Total revenue	1,849	1,965	2,066
Tampa Electric [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	1,018	1,046	1,067
Total gas revenue	0	0	0
Tampa Electric [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	506	562	582
Total gas revenue	0	0	0
Tampa Electric [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	133	156	161
Total gas revenue	0	0	0
Tampa Electric [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(25)	(49)	(2)
Tampa Electric [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	217	250	258
Total gas revenue	0	0	0
PGS [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	433	461	488
Total revenue	433	461	488
PGS [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	158	154	157
PGS [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	135	146	151
PGS [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	23	21	21
PGS [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
PGS [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	117	140	159
Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(4)	(4)	(3)
Total gas revenue	(6)	(18)	(27)
Total revenue	(10)	(22)	(30)
Eliminations [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	0	0	0
Eliminations [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	0	0	0
Eliminations [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Total gas revenue	0	0	0
Eliminations [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0
Eliminations [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(4)	(4)	(3)
Total gas revenue	$ (6)	$ (18)	$ (27)