Schedule II - Valuation and Qualifying Accounts and Reserves (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 4.2	$ 2.6	$ 4.5
Charged to Income	3.3	4.8	3.8
Other Charges	0	0	0
Payments & Deductions	2.8	3.2	5.7
Balance at End of Period	4.7	4.2	2.6
Tampa Electric Company [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	1.5	1.3	3.2
Charged to Income	3.3	3.4	3.8
Other Charges	0	0	0
Payments & Deductions	2.8	3.2	5.7
Balance at End of Period	$ 2.0	$ 1.5	$ 1.3