Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total revenues	$ 2,395.8	$ 2,419.2	$ 2,419.0
Depreciation and amortization	328.3	313.5	302.6
Total interest charges	105.8	109.6	106.6
Provision for income taxes	152.2	165.5	155.9
Net income	285.7	276.3	260.3
Total assets	8,082.6	7,708.6	7,274.3
Capital expenditures	726.8	686.6	671.0
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	2,395.8	2,419.2	2,419.0
Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	0.0	0.0	0.0
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(8.0)	(6.6)	(1.6)
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	(465.6)	(431.3)	(373.9)
Capital expenditures	0.0	0.0	0.0
Eliminations [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0	0.0
Eliminations [Member] | Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	(8.0)	(6.6)	(1.6)
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1,964.5	2,018.3	2,021.0
Depreciation and amortization	268.4	256.7	248.6
Total interest charges	91.1	95.1	92.8
Provision for income taxes	129.8	143.6	133.2
Net income	250.8	241.0	224.5
Total assets	7,356.9	7,003.8	6,565.4
Capital expenditures	594.3	592.6	582.1
Tampa Electric [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	1,963.6	2,017.7	2,020.5
Tampa Electric [Member] | Operating Segments [Member] | Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	0.9	0.6	0.5
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	439.3	407.5	399.6
Depreciation and amortization	59.9	56.8	54.0
Total interest charges	14.7	14.5	13.8
Provision for income taxes	22.4	21.9	22.7
Net income	34.9	35.3	35.8
Total assets	1,191.3	1,136.1	1,082.8
Capital expenditures	132.5	94.0	88.9
PGS [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	432.2	401.5	398.5
PGS [Member] | Operating Segments [Member] | Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	$ 7.1	$ 6.0	$ 1.1