Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Tampa Electric Company [Member]	Jun. 30, 2013 Tampa Electric Company [Member]	Jun. 30, 2014 Tampa Electric Company [Member]	Jun. 30, 2013 Tampa Electric Company [Member]	Jun. 30, 2014 Unbilled Revenues [Member]	Dec. 31, 2013 Unbilled Revenues [Member]	Jun. 30, 2014 Unbilled Revenues [Member] Tampa Electric Company [Member]	Dec. 31, 2013 Unbilled Revenues [Member] Tampa Electric Company [Member]
Summary Of Significant Accounting Policies [Line Items]
Unbilled revenues									$ 57.0	$ 46.7	$ 57.0	$ 46.7
Franchise fees and gross receipts taxes	$ 27.8	$ 26.7	$ 55.0	$ 52.1	$ 27.8	$ 26.7	$ 55.0	$ 52.1