Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues	$ 659.5	$ 693.0
Depreciation and amortization	89.8	85.5
Total interest charges	45.9	47.9
Internally allocated interest	0.0	0.0
Provision (benefit) for income taxes	35.7	39.9
Net income (loss) from continuing operations	73.7	63.8
Income (loss) from discontinued operations, net	0.1	(5.8)
Net income	73.8	58.0
Total assets	8,981.1		$ 8,933.5
Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	551.0	572.1
Depreciation and amortization	80.9	76.8
Total interest charges	27.5	27.0
Provision (benefit) for income taxes	36.7	36.6
Net income	63.3	62.8
Total assets	7,704.8		7,708.6
Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(5.5)	(2.0)
Depreciation and amortization	0.0	0.0
Total interest charges	(0.2)	(0.3)
Internally allocated interest	(0.2)	(0.3)
Provision (benefit) for income taxes	0.0	0.0
Net income (loss) from continuing operations	0.0	0.0
Income (loss) from discontinued operations, net	0.0	0.0
Net income	0.0	0.0
Total assets	(2,347.1)		(2,381.2)
Eliminations [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	(4.7)	(1.4)
Depreciation and amortization	0.0	0.0
Total interest charges	0.0	0.0
Provision (benefit) for income taxes	0.0	0.0
Net income	0.0	0.0
Total assets	(5.2)		(9.3)
Eliminations [Member] | Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	(4.7)	(1.4)
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	424.5	450.6
Depreciation and amortization	66.1	62.9
Total interest charges	23.8	23.5
Internally allocated interest	0.0	0.0
Provision (benefit) for income taxes	27.8	27.4
Net income (loss) from continuing operations	50.2	48.2
Income (loss) from discontinued operations, net	0.0	0.0
Net income	50.2	48.2
Total assets	6,988.2		7,003.8
Tampa Electric [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	424.5	450.6
Depreciation and amortization	66.1	62.9
Total interest charges	23.8	23.5
Provision (benefit) for income taxes	27.8	27.4
Net income	50.2	48.2
Total assets	6,600.4		6,620.2
Tampa Electric [Member] | Operating Segments [Member] | Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.3	0.2
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	131.2	122.9
Depreciation and amortization	14.8	13.9
Total interest charges	3.7	3.5
Internally allocated interest	0.0	0.0
Provision (benefit) for income taxes	8.9	9.2
Net income (loss) from continuing operations	13.1	14.6
Income (loss) from discontinued operations, net	0.0	0.0
Net income	13.1	14.6
Total assets	1,147.0		1,136.1
PGS [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	131.2	122.9
Depreciation and amortization	14.8	13.9
Total interest charges	3.7	3.5
Provision (benefit) for income taxes	8.9	9.2
Net income	13.1	14.6
Total assets	1,109.6		1,097.7
PGS [Member] | Operating Segments [Member] | Tampa Electric Company [Member] | Intracompany Sales [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	4.4	1.2
NMGC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	106.6	119.0
Depreciation and amortization	8.4	8.4
Total interest charges	3.0	3.3
Internally allocated interest	0.0	0.0
Provision (benefit) for income taxes	9.7	9.0
Net income (loss) from continuing operations	15.2	13.9
Income (loss) from discontinued operations, net	0.0	0.0
Net income	15.2	13.9
Total assets	1,210.9		1,229.7
TECO Coal [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Depreciation and amortization	0.0	0.0
Total interest charges	0.0	0.0
Internally allocated interest	0.0	0.0
Provision (benefit) for income taxes	0.0	0.0
Net income (loss) from continuing operations	0.0	0.0
Income (loss) from discontinued operations, net	0.0	(6.0)
Net income	0.0	(6.0)
Total assets	0.0		0.0
Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	2.7	2.5
Depreciation and amortization	0.5	0.3
Total interest charges	15.6	17.9
Internally allocated interest	0.2	0.3
Provision (benefit) for income taxes	(10.7)	(5.7)
Net income (loss) from continuing operations	(4.8)	(12.9)
Income (loss) from discontinued operations, net	0.1	0.2
Net income	(4.7)	(12.7)
Total assets	1,982.1		$ 1,945.1
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	659.5	693.0
Revenues - External [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	551.0	572.1
Revenues - External [Member] | Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Revenues - External [Member] | Eliminations [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Revenues - External [Member] | Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	423.4	449.8
Revenues - External [Member] | Tampa Electric [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	424.2	450.4
Revenues - External [Member] | PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	126.8	121.7
Revenues - External [Member] | PGS [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues	126.8	121.7
Revenues - External [Member] | NMGC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	106.6	119.0
Revenues - External [Member] | TECO Coal [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Revenues - External [Member] | Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	2.7	2.5
Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0
Sales to Affiliates [Member] | Eliminations [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	(5.5)	(2.0)
Sales to Affiliates [Member] | Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	1.1	0.8
Sales to Affiliates [Member] | PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	4.4	1.2
Sales to Affiliates [Member] | NMGC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0
Sales to Affiliates [Member] | TECO Coal [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	0.0	0.0
Sales to Affiliates [Member] | Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates/Intracompany sales	$ 0.0	$ 0.0