Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total revenues	$ 676.1	$ 693.8	$ 680.6	$ 693.0	$ 695.5	$ 687.2	$ 605.7	$ 578.0	$ 2,743.5	$ 2,566.4	$ 2,355.1
Depreciation and amortization									349.0	315.3	291.8
Total interest charges									186.4	171.1	161.4
Internally allocated interest									0.0	0.0	0.0
Provision for income taxes									155.3	138.9	112.6
Net income from continuing operations	51.0	64.9	61.5	63.8	27.4	73.0	57.6	48.4	241.2	206.4	188.7
Discontinued operations, net of tax									(67.7)	(76.0)	9.0
Net income	50.5	$ 53.2	$ 11.8	$ 58.0	10.8	$ 11.1	$ 58.4	$ 50.1	173.5	130.4	197.7
Goodwill	408.4				408.3				408.4	408.3	0.0
Total assets	8,961.1				8,726.2				8,961.1	8,726.2	7,448.0
Capital expenditures									739.7	703.8	526.1
Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									2,419.2	2,419.0	2,342.8
Depreciation and amortization									313.5	302.6	290.3
Total interest charges									109.6	106.6	105.3
Provision for income taxes									165.5	155.9	138.8
Net income									276.3	260.3	225.6
Total assets	7,726.7				7,274.3				7,726.7	7,274.3	6,875.8
Capital expenditures									686.6	671.0	501.3
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues									(9.5)	(2.4)	(2.2)
Depreciation and amortization									0.0	0.0	0.0
Total interest charges									(1.3)	(5.8)	(7.8)
Internally allocated interest									(1.3)	(5.8)	(7.8)
Provision for income taxes									0.0	0.0	0.0
Net income from continuing operations									0.0	0.0	0.0
Discontinued operations, net of tax									0.0	0.0	0.0
Net income									0.0	0.0	0.0
Goodwill	0.0				0.0				0.0	0.0
Total assets	(2,376.2)				(1,998.5)				(2,376.2)	(1,998.5)	(1,755.6)
Capital expenditures									0.0	0.0	0.0
Eliminations | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									(6.6)	(1.6)	(1.2)
Depreciation and amortization									0.0	0.0	0.0
Total interest charges									0.0	0.0	0.0
Provision for income taxes									0.0	0.0	0.0
Net income									0.0	0.0	0.0
Total assets	(9.4)				(7.1)				(9.4)	(7.1)	(8.9)
Capital expenditures									0.0	0.0	0.0
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues									2,743.5	2,566.4	2,355.1
Revenues - External [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									2,419.2	2,419.0	2,342.8
Revenues - External [Member] | Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues									0.0	0.0	0.0
Revenues - External [Member] | Eliminations | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									0.0	0.0	0.0
Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									0.0	0.0	0.0
Sales to Affiliates [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									0.0	0.0	0.0
Sales to Affiliates [Member] | Eliminations [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									(9.5)	(2.4)	(2.2)
Sales to Affiliates [Member] | Eliminations | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									(6.6)	(1.6)	(1.2)
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									2,018.3	2,021.0	1,950.5
Depreciation and amortization									256.7	248.6	238.8
Total interest charges									95.1	92.8	91.8
Internally allocated interest									0.0	0.0	0.0
Provision for income taxes									143.6	133.2	116.9
Net income from continuing operations									241.0	224.5	190.9
Discontinued operations, net of tax									0.0	0.0	0.0
Net income									241.0	224.5	190.9
Goodwill	0.0				0.0				0.0	0.0
Total assets	7,020.7				6,565.4				7,020.7	6,565.4	6,126.9
Capital expenditures									592.6	582.1	422.3
Tampa Electric [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									2,018.3	2,021.0	1,950.5
Depreciation and amortization									256.7	248.6	238.8
Total interest charges									95.1	92.8	91.8
Provision for income taxes									143.6	133.2	116.9
Net income									241.0	224.5	190.9
Total assets	6,637.1				6,234.4				6,637.1	6,234.4	5,895.4
Capital expenditures									592.6	582.1	422.3
Tampa Electric [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									2,014.9	2,019.9	1,949.6
Tampa Electric [Member] | Revenues - External [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									2,017.7	2,020.5	1,950.1
Tampa Electric [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									3.4	1.1	0.9
Tampa Electric [Member] | Sales to Affiliates [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									0.6	0.5	0.4
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									407.5	399.6	393.5
Depreciation and amortization									56.8	54.0	51.5
Total interest charges									14.5	13.8	13.5
Internally allocated interest									0.0	0.0	0.0
Provision for income taxes									21.9	22.7	21.9
Net income from continuing operations									35.3	35.8	34.7
Discontinued operations, net of tax									0.0	0.0	0.0
Net income									35.3	35.8	34.7
Goodwill	0.0				0.0				0.0	0.0
Total assets	1,137.4				1,082.8				1,137.4	1,082.8	1,021.2
Capital expenditures									94.0	88.9	79.0
PGS [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									407.5	399.6	393.5
Depreciation and amortization									56.8	54.0	51.5
Total interest charges									14.5	13.8	13.5
Provision for income taxes									21.9	22.7	21.9
Net income									35.3	35.8	34.7
Total assets	1,099.0				1,047.0				1,099.0	1,047.0	989.3
Capital expenditures									94.0	88.9	79.0
PGS [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									401.5	398.5	392.7
PGS [Member] | Revenues - External [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Total revenues									401.5	398.5	392.7
PGS [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									6.0	1.1	0.8
PGS [Member] | Sales to Affiliates [Member] | Operating Segments [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									6.0	1.1	0.8
NMGC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									316.5	137.5	0.0
Depreciation and amortization									33.8	11.0	0.0
Total interest charges									13.0	4.2	0.0
Internally allocated interest									0.0	0.0	0.0
Provision for income taxes									15.4	7.1	0.0
Net income from continuing operations									24.1	10.5	0.0
Discontinued operations, net of tax									0.0	0.0	0.0
Net income									24.1	10.5	0.0
Goodwill	408.4				408.3				408.4	408.3
Total assets	1,231.3				1,237.2				1,231.3	1,237.2	0.0
Capital expenditures									48.7	18.2	0.0
NMGC [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									316.5	137.5	0.0
NMGC [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									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
Depreciation and amortization									0.0	0.0	0.0
Total interest charges									0.0	0.0	0.0
Internally allocated interest									0.0	0.0	0.0
Provision for income taxes									0.0	0.0	0.0
Net income from continuing operations									0.0	0.0	0.0
Discontinued operations, net of tax									(69.6)	(82.0)	9.0
Net income									(69.6)	(82.0)	9.0
Goodwill	0.0				0.0				0.0	0.0
Total assets	0.0				227.7				0.0	227.7	316.3
Capital expenditures									3.7	14.6	22.4
TECO Coal [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									0.0	0.0	0.0
TECO Coal [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									0.0	0.0	0.0
Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									10.7	10.7	13.3
Depreciation and amortization									1.7	1.7	1.5
Total interest charges									65.1	66.1	63.9
Internally allocated interest									1.3	5.8	7.8
Provision for income taxes									(25.6)	(24.1)	(26.2)
Net income from continuing operations									(59.2)	(64.4)	(36.9)
Discontinued operations, net of tax									1.9	6.0	0.0
Net income									(57.3)	(58.4)	(36.9)
Goodwill	0.0				0.0				0.0	0.0
Total assets	$ 1,947.9				$ 1,611.6				1,947.9	1,611.6	1,739.2
Capital expenditures									0.7	0.0	2.4
Other [Member] | Revenues - External [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									10.6	10.5	12.8
Other [Member] | Sales to Affiliates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to affiliates									$ 0.1	$ 0.2	$ 0.5