Summary Of Significant Accounting Policies (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Tampa Electric Co [Member]	Jun. 30, 2011 Tampa Electric Co [Member]	Jun. 30, 2012 Tampa Electric Co [Member]	Jun. 30, 2011 Tampa Electric Co [Member]	Jun. 30, 2012 Unbilled Revenues [Member]	Dec. 31, 2011 Unbilled Revenues [Member]	Jun. 30, 2012 Franchise Fees And Gross Receipts [Member]	Jun. 30, 2011 Franchise Fees And Gross Receipts [Member]	Jun. 30, 2012 Franchise Fees And Gross Receipts [Member]	Jun. 30, 2011 Franchise Fees And Gross Receipts [Member]	Jun. 30, 2012 Franchise Fees And Gross Receipts [Member] Tampa Electric Co [Member]	Jun. 30, 2011 Franchise Fees And Gross Receipts [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Franchise Fees And Gross Receipts [Member] Tampa Electric Co [Member]	Jun. 30, 2011 Franchise Fees And Gross Receipts [Member] Tampa Electric Co [Member]	Jun. 30, 2012 Receivables [Member] Tampa Electric Co [Member]	Dec. 31, 2011 Receivables [Member] Tampa Electric Co [Member]
Summary Of Significant Accounting Policies [Line Items]
Unbilled revenues									$ 54.1	$ 50.2									$ 54.1	$ 50.2
Taxes, other than income	$ 57.1	$ 55.5	$ 113.1	$ 114.2	$ 46.9	$ 44.9	$ 92.3	$ 91.5			$ 28.3	$ 27.1	$ 54.4	$ 55.5	$ 28.3	$ 27.1	$ 54.4	$ 55.5