Long-Term Debt - Schedule of Maturities of Long-Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Maturities Of Long Term Debt [Line Items]
Total long-term debt maturities	$ 3,850.2	$ 3,628.5
Tampa Electric Company [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
Total long-term debt maturities	2,263.1	$ 2,097.1
Tampa Electric Company [Member] | PGS [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
2016	0.0
2017	0.0
2018	50.0
2019	0.0
2020	0.0
Thereafter	211.7
Total long-term debt maturities	261.7
Debt Maturities [Member] | PGS [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
2016	0.0
2017	0.0
2018	50.0
2019	0.0
2020	0.0
Thereafter	211.7
Total long-term debt maturities	261.7
Debt Maturities [Member] | TECO Finance [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
2016	250.0
2017	300.0
2018	250.0
2019	0.0
2020	300.0
Thereafter	0.0
Total long-term debt maturities	1,100.0
Debt Maturities [Member] | Tampa Electric Company [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
2016	83.3
2017	0.0
2018	254.2
2019	0.0
2020	0.0
Thereafter	1,666.7
Total long-term debt maturities	2,004.2
Debt Maturities [Member] | NMGC [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
2016	0.0
2017	0.0
2018	0.0
2019	0.0
2020	0.0
Thereafter	270.0
Total long-term debt maturities	270.0
Debt Maturities [Member] | NMGI [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
2016	0.0
2017	0.0
2018	0.0
2019	50.0
2020	0.0
Thereafter	150.0
Total long-term debt maturities	200.0
Debt Maturities [Member] | TECO Energy [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
2016	333.3
2017	300.0
2018	554.2
2019	50.0
2020	300.0
Thereafter	2,298.4
Total long-term debt maturities	$ 3,835.9