Accounting For Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011		Dec. 31, 2010
Net loss related to cash flow hedges and interest rate swaps in AOCI, after tax	$ (5.1)	[1]	$ (4.2)	[1]
Net pretax losses expected to be reclassified from regulatory assets or liabilities	29.5
Tampa Electric Co [Member]
Net loss related to cash flow hedges and interest rate swaps in AOCI, after tax	(4.8)	[2]	(5.3)	[2]
Net pretax losses expected to be reclassified from regulatory assets or liabilities	$ 29.5

[1] Net of tax benefit of $3.3 million and $2.7 million as of Sep. 30, 2011 and Dec. 31, 2010, respectively.

[2] Net of tax benefit of $3.0 million and $3.4 million as of Sep. 30, 2011 and Dec. 31, 2010, respectively.