Revenue - Summary of Disaggregates TEC Revenue by Major Source (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 509	$ 542	$ 970	$ 984
Total gas revenue	110	102	246	213
Total revenues	619	$ 644	1,216	$ 1,197
Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	241		471
Total gas revenue	35		91
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	140		272
Total gas revenue	37		81
Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	40		78
Total gas revenue	6		11
Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	24		23
Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	64		126
Total gas revenue	32		63
Tampa Electric [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	510		971
Total gas revenue	0		0
Total revenues	510		971
Tampa Electric [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	241		471
Total gas revenue	0		0
Tampa Electric [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	140		272
Total gas revenue	0		0
Tampa Electric [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	40		78
Total gas revenue	0		0
Tampa Electric [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	24		23
Tampa Electric [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	65		127
Total gas revenue	0		0
PGS [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	115		257
Total revenues	115		257
PGS [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	35		91
PGS [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	37		81
PGS [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	6		11
PGS [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
PGS [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	37		74
Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(1)		(1)
Total gas revenue	(5)		(11)
Total revenues	(6)		(12)
Eliminations [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	0		0
Eliminations [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	0		0
Eliminations [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Total gas revenue	0		0
Eliminations [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0		0
Eliminations [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(1)		(1)
Total gas revenue	$ (5)		$ (11)