Regulatory (Regulatory Assets And Related Recovery Periods) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	$ 387.0		$ 404.6
Clause Recoverable [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	41.2	[1]	45.2	[1]
Tampa Electric Co [Member] | Clause Recoverable [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	41.2	[1]	45.2	[1]
Components Of Rate Base [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	240.9	[2]	248.1	[2]
Tampa Electric Co [Member] | Components Of Rate Base [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	240.9	[2]	248.1	[2]
Regulatory Tax Asset [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	64.4	[3]	66.6	[3]
Tampa Electric Co [Member] | Regulatory Tax Asset [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	64.4	[4]	66.6	[4]
Capital Structure And Other [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	40.5	[3]	44.7	[3]
Tampa Electric Co [Member] | Capital Structure And Other [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	40.5	[4]	44.7	[4]
Tampa Electric Co [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	$ 387.0		$ 404.6

[1] To be recovered through cost recovery clauses approved by the FPSC on a dollar-for-dollar basis in the next year.

[2] Primarily reflects allowed working capital, which is included in rate base and earns a rate of return as permitted by the FPSC.

[3] "Regulatory tax assets" and "Capital structure and other" regulatory assets have a recoverable period longer than a fiscal year and are recognized over the period authorized by the regulatory agency. Also included are unamortized loan costs, which are amortized over the life of the related debt instruments. See footnotes 1 and 2 in the prior table for additional information.

[4] "Regulatory tax assets" and "Capital structure and other" regulatory assets have a recoverable period longer than a fiscal year and are recognized over the period authorized by the regulatory agency. Also included are unamortized loan costs, which are amortized over the life of the related debt instruments. See footnotes 1 and 2 in the prior table for additional information.