Accounting For Derivative Instruments And Hedging Activities (Energy Related Derivatives) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Current regulatory assets	$ 55.8		$ 62.7
Current regulatory liabilities	95.5		110.0
Long-term regulatory assets	331.2		341.9
Long-term regulatory liabilities	637.5		630.8
Regulatory assets	387.0		404.6
Regulatory liabilities	733.0		740.8
Tampa Electric Co [Member] | Energy Related Derivatives [Member]
Derivatives, Fair Value [Line Items]
Current regulatory assets	29.5	[1]
Current regulatory liabilities	0	[1]
Long-term regulatory assets	4.5	[1]
Long-term regulatory liabilities	0	[1]
Regulatory assets	34.0	[1]
Regulatory liabilities	0	[1]
Energy Related Derivatives [Member]
Derivatives, Fair Value [Line Items]
Current regulatory assets	29.5
Current regulatory liabilities	0
Long-term regulatory assets	4.5
Long-term regulatory liabilities	0
Regulatory assets	34.0
Regulatory liabilities	0
Tampa Electric Co [Member]
Derivatives, Fair Value [Line Items]
Current regulatory assets	55.8		62.7
Current regulatory liabilities	95.5		110.0
Long-term regulatory assets	331.2		341.9
Long-term regulatory liabilities	637.5		630.8
Regulatory assets	387.0		404.6
Regulatory liabilities	$ 733.0		$ 740.8

[1] Natural gas derivatives are deferred in accordance with accounting standards for regulated operations and all increases and decreases in the cost of natural gas supply are passed on to customers with the fuel recovery clause mechanism. As gains and losses are realized in future periods, they will be recorded as fuel costs in the Consolidated Condensed Statements of Income.