Accounting for Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Collateral posted with or received from any counterparties	$ 0	$ 0
Net loss related to cash flow hedges and interest rate swaps in AOCI, after tax	7.8	9.2
Net pretax losses expected to be reclassified from regulatory assets or liabilities	9.5
Diesel Fuel [Member]
Derivative [Line Items]
Maximum length of time hedging in future cash flow	Dec. 31, 2014
Natural Gas Contracts [Member]
Derivative [Line Items]
Maximum length of time hedging in future cash flow	Dec. 31, 2015
Tampa Electric Company [Member]
Derivative [Line Items]
Net loss related to cash flow hedges and interest rate swaps in AOCI, after tax	7.8	8.7
Net pretax losses expected to be reclassified from regulatory assets or liabilities	9.5
Interest Rate Swap [Member]
Derivative [Line Items]
Net loss related to cash flow hedges and interest rate swaps in AOCI, after tax	$ 7.8	$ 9.2