Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	6 Months Ended			0 Months Ended	6 Months Ended		15 Months Ended	48 Months Ended		1 Months Ended		3 Months Ended	48 Months Ended	3 Months Ended	4 Months Ended
	Jun. 05, 2012	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 05, 2012 Tampa Electric Co [Member]	Jun. 30, 2012 Tampa Electric Co [Member]	Jun. 30, 2011 Tampa Electric Co [Member]	Jun. 30, 2012 Tampa Electric Co [Member]	Mar. 15, 2012 Tampa Electric Co [Member]	Dec. 31, 2011 Tampa Electric Co [Member]	Mar. 15, 2012 HCIDA Bonds [Member]	Mar. 26, 2008 HCIDA Bonds [Member]	Mar. 31, 2012 HCIDA Bonds [Member]	Mar. 15, 2012 HCIDA Bonds [Member]	Mar. 01, 2011 PCIDA Bonds [Member]	Jun. 30, 2012 PCIDA Bonds [Member]
Debt Instrument [Line Items]
Interest at the initial term rate per annum									4.10%					5.00%	1.50%
Issuance of notes, maturity year		2042				2042
Issuance of notes, principal amount	$ 300				$ 300
Debt Instrument Principal Amount Market Price Percentage	99.724%				99.724%
Proceeds from notes net of issuance		296.2				296.2
Libor interest rate		25				25
Purchase in lieu of redemption		210.1	144.6			204.5	75.3	75.0			86.0	20.0	181.0			75.0
Long-term debt, carrying amount		3,165.7		3,075.8		2,087.7		2,087.7		1,992.3
Estimated fair value		$ 3,631.5		$ 3,435.3		$ 2,422.3		$ 2,422.3		$ 2,291.5