Regulatory (Regulatory Assets And Related Recovery Periods) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Regulatory Assets [Line Items]
Regulatory assets	$ 434.3		$ 451.8
Tampa Electric Co [Member]
Regulatory Assets [Line Items]
Regulatory assets	434.3		451.8
Clause Recoverable [Member]
Regulatory Assets [Line Items]
Regulatory assets	62.1	[1]	76.8	[1]
Clause Recoverable [Member] | Tampa Electric Co [Member]
Regulatory Assets [Line Items]
Regulatory assets	62.1	[1]	76.8	[1]
Components Of Rate Base [Member]
Regulatory Assets [Line Items]
Regulatory assets	258.5	[2]	264.9	[2]
Components Of Rate Base [Member] | Tampa Electric Co [Member]
Regulatory Assets [Line Items]
Regulatory assets	258.5	[2]	264.9	[2]
Regulatory Tax Assets [Member]
Regulatory Assets [Line Items]
Regulatory assets	62.5	[3],[4]	63.6	[3],[4]
Regulatory Tax Assets [Member] | Tampa Electric Co [Member]
Regulatory Assets [Line Items]
Regulatory assets	62.5	[3],[4]	63.6	[3],[4]
Capital Structure And Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	51.2	[3]	46.5	[3]
Capital Structure And Other [Member] | Tampa Electric Co [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 51.2	[3]	$ 46.5	[3]

[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] Primarily related to plant life and derivative positions.