Income Taxes - Schedule of Income Tax Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred income taxes
Total income tax expense	$ 108.8	$ 160.2	$ 153.9
Deferred income taxes
Amortization of investment tax credits	(0.3)	(0.3)	(0.4)
Income tax expense from continuing operations	108.9	137.8	142.7
Continuing Operations [Member]
Current income taxes
Current income taxes, Federal	2.2	15.7	0
Current income taxes, State	(3.5)	1.1	0.9
Deferred income taxes
Deferred income taxes, Federal	98.6	102.9	124.0
Deferred income taxes, State	11.9	18.4	18.2
Current income taxes
Current income taxes, Federal	2.2	15.7	0
Current income taxes, State	(3.5)	1.1	0.9
Deferred income taxes
Deferred income taxes, Federal	98.6	102.9	124.0
Deferred income taxes, State	11.9	18.4	18.2
Amortization of investment tax credits	(0.3)	(0.3)	(0.4)
Income tax expense from continuing operations	108.9	137.8	142.7
Discontinued Operations [Member]
Current income taxes
Current income taxes, Federal	0	0	0
Current income taxes, State	0	0	0
Deferred income taxes
Deferred income taxes, Federal	(0.1)	14.9	4.4
Deferred income taxes, State	0	0.7	(0.3)
Income tax expense from discontinued operations	(0.1)	22.4	11.2
Current income taxes
Current income taxes, Federal	0	0	0
Current income taxes, Foreign	0	6.8	7.4
Current income taxes, State	0	0	0
Deferred income taxes
Deferred income taxes, Federal	(0.1)	14.9	4.4
Deferred income taxes, State	0	0.7	(0.3)
Current income taxes, Foreign	0	0	(0.3)
Tampa Electric Company [Member]
Current income taxes
Current income taxes, Federal	19.4	(19.5)	(30.7)
Current income taxes, State	1.3	5.6	2.9
Deferred income taxes
Deferred income taxes, Federal	99.8	141.2	155.6
Deferred income taxes, State	18.6	14.7	18.0
Current income taxes
Current income taxes, Federal	19.4	(19.5)	(30.7)
Current income taxes, State	1.3	5.6	2.9
Deferred income taxes
Deferred income taxes, Federal	99.8	141.2	155.6
Deferred income taxes, State	18.6	14.7	18.0
Amortization of investment tax credits	(0.3)	(0.3)	(0.4)
Income tax expense from continuing operations	$ 138.8	$ 141.7	$ 145.4