Short-Term Debt - Additional Information (Detail) - USD ($)		9 Months Ended
	Mar. 24, 2015	Sep. 30, 2015	Dec. 31, 2014
Line Of Credit Facility [Line Items]
Line of Credit Facility maximum borrowing capacity		$ 900,000,000	$ 900,000,000
Tampa Electric Company [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate			0.70%
Line of Credit Facility maximum borrowing capacity		475,000,000	$ 475,000,000
Outstanding borrowings		0
Tampa Electric Company [Member] | 1-year Accounts Receivable Facility [Member]
Line Of Credit Facility [Line Items]
Line of Credit Facility maximum borrowing capacity		$ 150,000,000
Credit facility maturity date	Mar. 23, 2018
Credit Facility amendment date	Mar. 24, 2015
Tampa Electric Company [Member] | 1-year Accounts Receivable Facility [Member] | Before Amendment and Restatement
Line Of Credit Facility [Line Items]
Credit facility maturity date	Apr. 14, 2015
TECO Energy [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.28%	1.16%
TECO Finance [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.28%	1.16%
New Mexico Gas Company [Member]
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.28%	1.16%
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%