Short-Term Debt - Credit Facilities (Detail) (USD $) In Millions, unless otherwise specified	Feb. 15, 2013	Dec. 31, 2012	Dec. 31, 2011	Oct. 25, 2011	Mar. 25, 2011
Line of Credit Facility [Line Items]
Credit Facilities	$ 150.0	$ 675.0	$ 675.0	$ 200.0
Borrowings Outstanding		0	0
Letters of Credit Outstanding		1.5	0.7
TAMPA ELECTRIC CO [Member]
Line of Credit Facility [Line Items]
Credit Facilities	150.0	475.0	475.0	200.0	200.0
Borrowings Outstanding		0	0
Letters of Credit Outstanding		1.5	0.7
TAMPA ELECTRIC CO [Member] | 5-year facility [Member]
Line of Credit Facility [Line Items]
Credit Facilities		325.0	325.0
Borrowings Outstanding		0	0
Letters of Credit Outstanding		1.5	0.7
TAMPA ELECTRIC CO [Member] | 1-year accounts receivable facility [Member]
Line of Credit Facility [Line Items]
Credit Facilities		150.0	150.0
Borrowings Outstanding		0	0
Letters of Credit Outstanding		0	0
Teco Energy [Member] | 5-year facility [Member]
Line of Credit Facility [Line Items]
Credit Facilities		200.0	200.0
Borrowings Outstanding		0	0
Letters of Credit Outstanding		$ 0	$ 0