Short-Term Debt - Additional Information (Detail) - USD ($)		9 Months Ended
	Mar. 14, 2016	Sep. 30, 2016	Dec. 31, 2015
Line Of Credit Facility [Line Items]
Line of Credit Facility maximum borrowing capacity		$ 1,300,000,000	$ 900,000,000
Tampa Electric Company [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.32%	0.89%
Line of Credit Facility maximum borrowing capacity		$ 475,000,000	$ 475,000,000
TECO Energy [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.71%	1.29%
TECO Finance [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.71%	1.29%
Interest rate description		provides for interest to accrue at variable rates based on the London interbank deposit rate plus a margin, or, as an alternative to such interest rate, at an interest rate equal to a margin plus the higher of JPMorgan Chase Bank’s prime rate, the federal funds rate plus 50 basis points, or the one-month London interbank deposit rate plus 1.00%.
TECO Finance [Member] | 1-year Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Line of Credit Facility maximum borrowing capacity	$ 400,000,000
Credit facility maturity date	Mar. 14, 2017
TECO Finance [Member] | Federal Funds Rate [Member]
Line Of Credit Facility [Line Items]
Basis spread on referenced interest rate	0.50%
TECO Finance [Member] | London Interbank Deposit Rate [Member]
Line Of Credit Facility [Line Items]
Basis spread on referenced interest rate	1.00%
New Mexico Gas Company [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.71%	1.29%
Minimum [Member] | Tampa Electric Company [Member]
Line Of Credit Facility [Line Items]
Commitment fees, percentage		0.125%
Maximum [Member] | Tampa Electric Company [Member]
Line Of Credit Facility [Line Items]
Commitment fees, percentage		0.30%