Short-Term Debt - Credit Facilities (Parenthetical) (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Tampa Electric Company [Member] | 5-year Facility [Member]
Line Of Credit Facility [Line Items]
Credit facility maturity date	Dec. 17, 2018	Dec. 17, 2018
Tampa Electric Company [Member] | 3-year Accounts Receivable Facility [Member]
Line Of Credit Facility [Line Items]
Credit facility maturity date	Mar. 23, 2018	Mar. 23, 2018
TECO Energy [Member] | 5-year Facility [Member]
Line Of Credit Facility [Line Items]
Credit facility maturity date	Dec. 17, 2018	Dec. 17, 2018
TECO Energy [Member] | 1-year Term Facility [Member]
Line Of Credit Facility [Line Items]
Credit facility maturity date	Mar. 14, 2017	Mar. 14, 2017
New Mexico Gas Company [Member] | 5-year Facility [Member]
Line Of Credit Facility [Line Items]
Credit facility maturity date	Dec. 17, 2018	Dec. 17, 2018