Short-Term Debt - Credit Facilities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Feb. 15, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]
Credit Facilities	$ 675.0		$ 675.0
Borrowings Outstanding	0		0
Letters of Credit Outstanding	1.5		1.5
Tampa Electric Company [Member]
Line of Credit Facility [Line Items]
Credit Facilities	475.0		475.0
Borrowings Outstanding	0		0
Letters of Credit Outstanding	1.5		1.5
Tampa Electric Company [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		1.5
Tampa Electric Company [Member] | 1-year Accounts Receivable Facility [Member]
Line of Credit Facility [Line Items]
Credit Facilities	150.0	150.0	150.0
Borrowings Outstanding	0		0
Letters of Credit Outstanding	0		0
TECO ENERGY, INC. [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