Commitments and Contingencies - Additional Information (Detail) $ in Millions			12 Months Ended
	Dec. 19, 2013 USD ($)	Feb. 08, 2011 Customer Lawsuit InsuranceCarrier	Dec. 31, 2015 USD ($) Claims	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2015 USD ($)	Mar. 31, 2011 Customer
Long Term Commitments [Line Items]
Gas supply disruption of high utility customers | Customer		28,700					32,000
Number of class actions settled | Claims			2
Number of lawsuits for insurance carriers | Lawsuit		2
Number of insurance carriers | InsuranceCarrier		18
Total rental expense and leases			$ 15.3	$ 13.7	$ 7.6
Letters of Credit Outstanding			2.2	2.3		$ 93.8
Tampa Electric Company [Member]
Long Term Commitments [Line Items]
Total rental expense and leases			3.8	4.1	$ 2.3
Letters of Credit Outstanding			0.5	$ 0.6
PGS [Member]
Long Term Commitments [Line Items]
Total potential penalties			3.9
Ultimate financial liability to superfund sites and former MGP sites			33.9
PGS [Member] | Tampa Electric Company [Member]
Long Term Commitments [Line Items]
Total potential penalties			3.9
Ultimate financial liability to superfund sites and former MGP sites			$ 33.9
TECO Guatemala Holdings, LLC v. The Republic of Guatemala [Member]
Long Term Commitments [Line Items]
Litigation settlement amount	$ 7.5
Damages awarded	$ 21.1
TECO Guatemala Holdings, LLC v. The Republic of Guatemala [Member] | U.S. prime rate plus [Member]
Long Term Commitments [Line Items]
Litigation settlement interest	2.00%