Revenue - Summary of Disaggregates TEC Revenue by Major Source (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 520	$ 509	$ 931	$ 970
Total gas revenue	107	110	235	246
Total revenue	627	619	1,166	1,216
Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	261	241	467	471
Total gas revenue	36	35	86	91
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	141	140	261	272
Total gas revenue	35	37	77	81
Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	42	40	76	78
Total gas revenue	6	6	11	11
Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	17	24	10	23
Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	59	64	117	126
Total gas revenue	30	32	61	63
Tampa Electric [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	521	510	933	971
Total gas revenue	0	0	0	0
Total revenue	521	510	933	971
Tampa Electric [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	261	241	467	471
Total gas revenue	0	0	0	0
Tampa Electric [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	141	140	261	272
Total gas revenue	0	0	0	0
Tampa Electric [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	42	40	76	78
Total gas revenue	0	0	0	0
Tampa Electric [Member] | Regulatory Deferrals and Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	17	24	10	23
Tampa Electric [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	60	65	119	127
Total gas revenue	0	0	0	0
PGS [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	111	115	243	257
Total revenue	111	115	243	257
PGS [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	36	35	86	91
PGS [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	35	37	77	81
PGS [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	0	0	0	0
Total gas revenue	6	6	11	11
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	34	37	69	74
Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(1)	(1)	(2)	(1)
Total gas revenue	(4)	(5)	(8)	(11)
Total revenue	(5)	(6)	(10)	(12)
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)	(1)
Total gas revenue	$ (4)	$ (5)	$ (8)	$ (11)