Employee Postretirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Jan. 01, 2015
Defined Benefit Plan Disclosure [Line Items]
Reclassification of AOCI to net income as part of periodic benefit expense	$ 0.8	$ 0.6
Reclassification of regulatory assets to net income as part of periodic benefit expense	2.2	2.5
TECO Coal [Member]
Defined Benefit Plan Disclosure [Line Items]
Black lung liability	24.8		24.7
Expenses related to black lung liability	0	0
Settlement charge, related to unfunded black lung obligations	7.7
Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Long-term EROA	7.00%
Employer contributions	11.0	13.0
Reclassification of regulatory assets to net income as part of periodic benefit expense	1.9	2.5
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Long-term EROA	7.00%
Discount rate	4.256%
Employer contributions	14.9	16.0
Net pension expense	4.4	5.1
Pension Benefits [Member] | Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.256%
Net pension expense	2.6	3.8
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate				4.206%
Net pension expense	2.0	3.2
Other Postretirement Benefits [Member] | Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate				4.206%
Net pension expense	$ 1.4	$ 2.6