Accounting for Derivative Instruments and Hedging Activities (Narrative) (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011		Dec. 31, 2010
Net loss related to cash flow hedges and interest rate swaps in AOCI, after tax	$ (3.3)	[1]	$ (4.2)	[1]
Net pretax losses expected to be reclassified from regulatory assets or liabilities	12.3
Tampa Electric Co [Member]
Net loss related to cash flow hedges and interest rate swaps in AOCI, after tax	(5.0)	[2]	(5.3)	[2]
Net pretax losses expected to be reclassified from regulatory assets or liabilities	$ 12.3

[1] Net of tax benefit of $2.2 million and $ 2.7 million as of Jun. 30, 2011 and Dec. 31, 2010, respectively.

[2] Net of tax benefit of $3.1 million and $3.4 million as of Jun. 30, 2011 and Dec. 31, 2010, respectively.