Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues	$ 726.7	$ 693.8	$ 2,038.5	$ 2,067.4
Total interest charges	43.9	46.1	133.6	140.4
Net income (loss) from continuing operations	69.4	64.9	148.6	190.2
Income (loss) from discontinued operations, net	0.0	(11.7)	(0.1)	(67.2)
Net income	69.4	53.2	148.5	123.0
Total assets	9,223.7		9,223.7		$ 8,933.5
Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	689.1	648.2	1,838.9	1,844.9
Total interest charges	26.1	27.8	79.8	82.0
Net income	100.6	88.3	239.6	226.4
Total assets	7,953.8		7,953.8		7,708.6
Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0	0.0	0.0
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(1.3)	(2.8)	(9.9)	(7.0)
Total interest charges	(0.2)	(0.3)	(0.7)	(1.0)
Net income (loss) from continuing operations	0.0	0.0	0.0	0.0
Income (loss) from discontinued operations, net	0.0	0.0	0.0	0.0
Net income	0.0	0.0	0.0	0.0
Total assets	(2,444.9)		(2,444.9)		(2,381.2)
Eliminations [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	(0.5)	(2.1)	(7.5)	(4.8)
Total interest charges	0.0	0.0	(0.1)	0.0
Net income	0.0	0.0	0.0	0.0
Total assets	(452.6)		(452.6)		(431.3)
Eliminations [Member] | Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	(0.5)	(2.1)	(7.5)	(4.8)
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	726.7	693.8	2,038.5	2,067.4
Revenues - External [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	689.1	648.2	1,838.9	1,844.9
Revenues - External [Member] | Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0	0.0	0.0
Revenues - External [Member] | Eliminations [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0	0.0	0.0
Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0	0.0	0.0
Sales to Affiliates [Member] | Eliminations [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	(1.3)	(2.8)	(9.9)	(7.0)
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	585.9	560.2	1,509.6	1,543.2
Total interest charges	22.4	24.1	68.8	71.2
Net income (loss) from continuing operations	94.1	82.1	212.9	198.0
Income (loss) from discontinued operations, net	0.0	0.0	0.0	0.0
Net income	94.1	82.1	212.9	198.0
Total assets	7,244.9		7,244.9		7,003.8
Tampa Electric [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	585.9	560.2	1,509.6	1,543.2
Total interest charges	22.4	24.1	68.8	71.2
Net income	94.1	82.1	212.9	198.0
Total assets	7,244.9		7,244.9		7,003.8
Tampa Electric [Member] | Operating Segments [Member] | Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.1	0.7	0.3
Tampa Electric [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	585.1	559.4	1,506.6	1,540.8
Tampa Electric [Member] | Revenues - External [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	585.9	560.1	1,508.9	1,542.9
Tampa Electric [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.8	0.8	3.0	2.4
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	103.7	90.1	336.8	306.5
Total interest charges	3.7	3.7	11.1	10.8
Net income (loss) from continuing operations	6.5	6.2	26.7	28.4
Income (loss) from discontinued operations, net	0.0	0.0	0.0	0.0
Net income	6.5	6.2	26.7	28.4
Total assets	1,161.5		1,161.5		1,136.1
PGS [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	103.7	90.1	336.8	306.5
Total interest charges	3.7	3.7	11.1	10.8
Net income	6.5	6.2	26.7	28.4
Total assets	1,161.5		1,161.5		1,136.1
PGS [Member] | Operating Segments [Member] | Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.5	2.0	6.8	4.5
PGS [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	103.3	88.1	330.0	302.0
PGS [Member] | Revenues - External [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	103.2	88.1	330.0	302.0
PGS [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.4	2.0	6.8	4.5
New Mexico Gas Co. [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	35.7	43.7	194.0	216.7
Total interest charges	2.8	3.2	9.1	9.8
Net income (loss) from continuing operations	(19.8)	(2.8)	(4.8)	11.0
Income (loss) from discontinued operations, net	0.0	0.0	0.0	0.0
Net income	(19.8)	(2.8)	(4.8)	11.0
Total assets	1,230.4		1,230.4		1,229.7
New Mexico Gas Co. [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	35.7	43.7	194.0	216.7
New Mexico Gas Co. [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0	0.0	0.0
TECO Coal [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0	0.0	0.0
Total interest charges	0.0	0.0	0.0	0.0
Net income (loss) from continuing operations	0.0	0.0	0.0	0.0
Income (loss) from discontinued operations, net	0.0	(12.1)	0.0	(69.6)
Net income	0.0	(12.1)	0.0	(69.6)
Total assets	0.0		0.0		0.0
TECO Coal [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0	0.0	0.0
TECO Coal [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0	0.0	0.0
Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	2.7	2.6	8.0	8.0
Total interest charges	15.2	15.4	45.3	49.6
Net income (loss) from continuing operations	(11.4)	(20.6)	(86.2)	(47.2)
Income (loss) from discontinued operations, net	0.0	0.4	(0.1)	2.4
Net income	(11.4)	(20.2)	(86.3)	(44.8)
Total assets	2,031.8		2,031.8		$ 1,945.1
Other [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	2.6	2.6	7.9	7.9
Other [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	$ 0.1	$ 0.0	$ 0.1	$ 0.1