Regulatory (Schedule Of Regulatory Assets And Regulatory Liabilities) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended				9 Months Ended																																																																																																1 Months Ended
	Jun. 30, 2011	Apr. 30, 2011	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 Maximum [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Maximum [Member]	Sep. 30, 2011 Minimum [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Minimum [Member]	Sep. 30, 2011 Regulatory Tax Asset [Member]		Dec. 31, 2010 Regulatory Tax Asset [Member]		Sep. 30, 2011 Tampa Electric Co [Member] Regulatory Tax Asset [Member]		Dec. 31, 2010 Tampa Electric Co [Member] Regulatory Tax Asset [Member]		Sep. 30, 2011 Cost Recovery Clauses [Member]	Dec. 31, 2010 Cost Recovery Clauses [Member]	Sep. 30, 2011 Cost Recovery Clauses [Member]	Dec. 31, 2010 Cost Recovery Clauses [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Cost Recovery Clauses [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Cost Recovery Clauses [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Cost Recovery Clauses [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Cost Recovery Clauses [Member]	Sep. 30, 2011 Postretirement Benefit Asset [Member]	Dec. 31, 2010 Postretirement Benefit Asset [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Postretirement Benefit Asset [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Postretirement Benefit Asset [Member]	Sep. 30, 2011 Environmental Remediation [Member]	Dec. 31, 2010 Environmental Remediation [Member]	Sep. 30, 2011 Environmental Remediation [Member]	Dec. 31, 2010 Environmental Remediation [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Environmental Remediation [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Environmental Remediation [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Environmental Remediation [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Environmental Remediation [Member]	Sep. 30, 2011 Competitive Rate Adjustment [Member]	Dec. 31, 2010 Competitive Rate Adjustment [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Competitive Rate Adjustment [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Competitive Rate Adjustment [Member]	Sep. 30, 2011 Other Regulatory Asset [Member]	Dec. 31, 2010 Other Regulatory Asset [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Other Regulatory Asset [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Other Regulatory Asset [Member]	Sep. 30, 2011 Total Other Regulatory Assets [Member]	Dec. 31, 2010 Total Other Regulatory Assets [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Total Other Regulatory Assets [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Total Other Regulatory Assets [Member]	Sep. 30, 2011 Deferred Income Tax Charges [Member]		Dec. 31, 2010 Deferred Income Tax Charges [Member]		Sep. 30, 2011 Deferred Income Tax Charges [Member]		Dec. 31, 2010 Deferred Income Tax Charges [Member]		Sep. 30, 2011 Tampa Electric Co [Member] Deferred Income Tax Charges [Member]		Dec. 31, 2010 Tampa Electric Co [Member] Deferred Income Tax Charges [Member]		Sep. 30, 2011 Tampa Electric Co [Member] Deferred Income Tax Charges [Member]		Dec. 31, 2010 Tampa Electric Co [Member] Deferred Income Tax Charges [Member]		Sep. 30, 2011 Deferred Bond Refinancing Costs [Member]		Dec. 31, 2010 Deferred Bond Refinancing Costs [Member]		Sep. 30, 2011 Tampa Electric Co [Member] Deferred Bond Refinancing Costs [Member]		Dec. 31, 2010 Tampa Electric Co [Member] Deferred Bond Refinancing Costs [Member]		Sep. 30, 2011 Deferred Gain On Property Sales [Member]		Dec. 31, 2010 Deferred Gain On Property Sales [Member]		Sep. 30, 2011 Tampa Electric Co [Member] Deferred Gain On Property Sales [Member]		Dec. 31, 2010 Tampa Electric Co [Member] Deferred Gain On Property Sales [Member]		Sep. 30, 2011 Total Other Regulatory Liabilities [Member]	Dec. 31, 2010 Total Other Regulatory Liabilities [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Total Other Regulatory Liabilities [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Total Other Regulatory Liabilities [Member]	Sep. 30, 2011 Storm Damage Reserve [Member]	Dec. 31, 2010 Storm Damage Reserve [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Storm Damage Reserve [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Storm Damage Reserve [Member]	Sep. 30, 2011 Provision For Stipulation And Other [Member]		Dec. 31, 2010 Provision For Stipulation And Other [Member]		Sep. 30, 2011 Tampa Electric Co [Member] Provision For Stipulation And Other [Member]		Dec. 31, 2010 Tampa Electric Co [Member] Provision For Stipulation And Other [Member]		Sep. 30, 2011 Accumulated Reserve-Cost Of Removal [Member]	Dec. 31, 2010 Accumulated Reserve-Cost Of Removal [Member]	Sep. 30, 2011 Tampa Electric Co [Member] Accumulated Reserve-Cost Of Removal [Member]	Dec. 31, 2010 Tampa Electric Co [Member] Accumulated Reserve-Cost Of Removal [Member]	Jun. 30, 2011 Tampa Electric Co [Member]	Apr. 30, 2011 Tampa Electric Co [Member]	Sep. 30, 2011 Tampa Electric Co [Member]	Dec. 31, 2010 Tampa Electric Co [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets			$ 387.0	$ 404.6					$ 64.4	[1]	$ 66.6	[1]	$ 64.4	[2]	$ 66.6	[2]	$ 38.0	$ 41.9			$ 38.0	$ 41.9			$ 228.9	$ 237.5	$ 228.9	$ 237.5	$ 23.2	$ 23.6			$ 23.2	$ 23.6			$ 3.2	$ 3.3	$ 3.2	$ 3.3	$ 17.1	$ 16.3	$ 17.1	$ 16.3	$ 322.6	$ 338.0	$ 322.6	$ 338.0	$ 64.4	[3]	$ 66.6	[3]					$ 64.4	[3]	$ 66.6	[3]					$ 12.2	[4]	$ 15.4	[4]	$ 12.2	[4]	$ 15.4	[4]																															$ 387.0	$ 404.6
Current regulatory assets			55.8	62.7																																																																																																			55.8	62.7
Long-term regulatory assets			331.2	341.9																																																																																																			331.2	341.9
Regulatory liabilities			733.0	740.8															70.7	76.2			70.7	76.2							21.2	21.2			21.2	21.2																	16.7	[3]	17.7	[3]					16.7	[3]	17.7	[3]									5.4	[5]	6.3	[5]	5.4	[5]	6.3	[5]	716.3	723.1	716.3	723.1	41.5	37.4	41.5	37.4	0.8	[6]	9.8	[6]	0.8	[6]	9.8	[6]	576.7	572.2	576.7	572.2			733.0	740.8
Current regulatory liabilities			95.5	110.0																																																																																																			95.5	110.0
Long-term regulatory liabilities			637.5	630.8																																																																																																			637.5	630.8
Amortization period					5	5	4	4
Stipulation earnings	11.75%	11.75%																																																																																																				11.75%
One time reduction to customers bills	$ 6.2	$ 3.0																																																																																																			$ 6.2	$ 3.0

[1] "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.

[2] "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.

[3] Primarily related to plant life and derivative positions.

[4] Amortized over the term of the related debt instruments.

[5] Amortized over a 4 or 5-year period with various ending dates.

[6] Includes a provision to reflect the FPSC-approved PGS stipulation regarding PGS's 2010 earnings above 11.75%. A one-time credit to customer bills totaling $3.0 million was applied in April 2011 and the $6.2 million remaining balance of the 2010 earnings above 11.75% was credited to accumulated depreciation reserves in June 2011.