Commitments and Contingencies - Letters of Credit and Guarantees (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Guarantor Obligations [Line Items]
2014	$ 0
2015-2018	0.7
After 2018	96.9
Total	97.6
Liabilities Recognized at Jun 30, 2014	0.7
Tampa Electric Company [Member]
Guarantor Obligations [Line Items]
2014	0
2015-2018	0
After 2018	0.7
Total	0.7
Liabilities Recognized at Jun 30, 2014	0.1
Tampa Electric Company [Member] | Letters of Credit [Member]
Guarantor Obligations [Line Items]
2014	0
2015-2018	0
After 2018	0.7
Total	0.7
Liabilities Recognized at Jun 30, 2014	0.1
TECO Coal [Member] | Fuel Purchase Related [Member]
Guarantor Obligations [Line Items]
2014	0
2015-2018	0.7
After 2018	4.0
Total	4.7
Liabilities Recognized at Jun 30, 2014	0.6
Other Subsidiaries [Member] | Fuel Purchase / Energy Management [Member]
Guarantor Obligations [Line Items]
2014	0
2015-2018	0
After 2018	92.9
Total	92.9
Liabilities Recognized at Jun 30, 2014	$ 0.1