Regulatory (Schedule Of Regulatory Assets And Regulatory Liabilities) (Detail) (USD $) In Millions, unless otherwise specified					6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Tampa Electric Co [Member]	Dec. 31, 2011 Tampa Electric Co [Member]	Jun. 30, 2012 Minimum [Member]	Jun. 30, 2012 Maximum [Member]	Jun. 30, 2012 Regulatory Tax Assets [Member]		Dec. 31, 2011 Regulatory Tax Assets [Member]		Jun. 30, 2012 Regulatory Tax Assets [Member] Tampa Electric Co [Member]		Dec. 31, 2011 Regulatory Tax Assets [Member] Tampa Electric Co [Member]		Jun. 30, 2012 Cost-Recovery Clauses [Member]	Dec. 31, 2011 Cost-Recovery Clauses [Member]	Jun. 30, 2012 Cost-Recovery Clauses [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Cost-Recovery Clauses [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Postretirement Benefit Asset [Member]	Dec. 31, 2011 Postretirement Benefit Asset [Member]	Jun. 30, 2012 Postretirement Benefit Asset [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Postretirement Benefit Asset [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Loss on Reacquired Debt [Member]		Dec. 31, 2011 Loss on Reacquired Debt [Member]		Jun. 30, 2012 Loss on Reacquired Debt [Member] Tampa Electric Co [Member]		Dec. 31, 2011 Loss on Reacquired Debt [Member] Tampa Electric Co [Member]		Jun. 30, 2012 Environmental Restoration Costs [Member]	Dec. 31, 2011 Environmental Restoration Costs [Member]	Jun. 30, 2012 Environmental Restoration Costs [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Environmental Restoration Costs [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Competitive Rate Adjustment [Member]	Dec. 31, 2011 Competitive Rate Adjustment [Member]	Jun. 30, 2012 Competitive Rate Adjustment [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Competitive Rate Adjustment [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Other Regulatory Asset [Member]	Dec. 31, 2011 Other Regulatory Asset [Member]	Jun. 30, 2012 Other Regulatory Asset [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Other Regulatory Asset [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Total Other Regulatory Assets [Member]	Dec. 31, 2011 Total Other Regulatory Assets [Member]	Jun. 30, 2012 Total Other Regulatory Assets [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Total Other Regulatory Assets [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Deferred Income Tax Charges [Member]		Dec. 31, 2011 Deferred Income Tax Charges [Member]		Jun. 30, 2012 Deferred Income Tax Charges [Member] Tampa Electric Co [Member]		Dec. 31, 2011 Deferred Income Tax Charges [Member] Tampa Electric Co [Member]		Jun. 30, 2012 Storm Costs [Member]	Dec. 31, 2011 Storm Costs [Member]	Jun. 30, 2012 Storm Costs [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Storm Costs [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Deferred Gain On Property Sales [Member]		Dec. 31, 2011 Deferred Gain On Property Sales [Member]		Jun. 30, 2012 Deferred Gain On Property Sales [Member] Tampa Electric Co [Member]		Dec. 31, 2011 Deferred Gain On Property Sales [Member] Tampa Electric Co [Member]		Jun. 30, 2012 Revenue Subject To Refund [Member]	Dec. 31, 2011 Revenue Subject To Refund [Member]	Jun. 30, 2012 Revenue Subject To Refund [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Revenue Subject To Refund [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Asset Retirement Obligation Costs [Member]	Dec. 31, 2011 Asset Retirement Obligation Costs [Member]	Jun. 30, 2012 Asset Retirement Obligation Costs [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Asset Retirement Obligation Costs [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Total Other Regulatory Liabilities [Member]	Dec. 31, 2011 Total Other Regulatory Liabilities [Member]	Jun. 30, 2012 Total Other Regulatory Liabilities [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Total Other Regulatory Liabilities [Member] Tampa Electric Co [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 434.3	$ 451.8	$ 434.3	$ 451.8			$ 62.5	[1],[2]	$ 63.6	[1],[2]	$ 62.5	[1],[2]	$ 63.6	[1],[2]	$ 58.6	$ 73.3	$ 58.6	$ 73.3	$ 245.2	$ 252.4	$ 245.2	$ 252.4	$ 9.1	[3]	$ 11.1	[3]	$ 9.1	[3]	$ 11.1	[3]	$ 37.7	$ 30.5	$ 37.7	$ 30.5	$ 3.5	$ 3.5	$ 3.5	$ 3.5	$ 17.7	$ 17.4	$ 17.7	$ 17.4	$ 371.8	$ 388.2	$ 371.8	$ 388.2
Less: Current portion	83.2	87.3	83.2	87.3
Long-term regulatory assets	351.1	364.5	351.1	364.5
Regulatory liabilities	737.5	734.0	737.5	734.0											58.7	61.4	58.7	61.4													28.4	28.4	28.4	28.4													15.3	[1]	16.0	[1]	15.3	[1]	16.0	[1]	47.6	43.6	47.6	43.6	4.1	[4]	5.0	[4]	4.1	[4]	5.0	[4]	1.0	0.8	1.0	0.8	582.4	578.8	582.4	578.8	722.2	718.0	722.2	718.0
Less: Current portion	83.4	86.2	83.4	86.2
Long-term regulatory liabilities	$ 654.1	$ 647.8	$ 654.1	$ 647.8
Amortization period					4	5

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

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

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