Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 553	$ 551
Total interest charges	29	28
Net income	56	63
Total assets	8,105		$ 8,083
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	553	551
Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	0	0
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(1)	(5)
Total interest charges	0	0
Net income	0	0
Total assets	(496)		(465)
Eliminations [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	0	0
Eliminations [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	(1)	(5)
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	442	425
Total interest charges	25	24
Net income	42	50
Total assets	7,388		7,357
Tampa Electric [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	442	424
Tampa Electric [Member] | Operating Segments [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	0	1
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	112	131
Total interest charges	4	4
Net income	14	13
Total assets	1,213		$ 1,191
PGS [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	111	127
PGS [Member] | Operating Segments [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Intracompany sales	$ 1	$ 4