Commitments And Contingencies (Letters Of Credit And Guarantees) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012
Letters Of Credit [Member]
Product Liability Contingency [Line Items]
2012	$ 0	[1]
2013-2016	0	[1]
After 2016	0.7	[1],[2]
Total	0.7	[1]
Liabilities Recognized at Jun. 30, 2012	0.2	[1]
Tampa Electric Co [Member] | Letters Of Credit [Member]
Product Liability Contingency [Line Items]
2012	0	[3]
2013-2016	0	[3]
After 2016	0.7	[3],[4]
Total	0.7	[3]
Liabilities Recognized at Jun. 30, 2012	0.2	[3]
Teco Coal [Member] | Guarantees: Fuel Purchase Related [Member]
Product Liability Contingency [Line Items]
2012	0	[1]
2013-2016	0	[1]
After 2016	5.4	[1],[2]
Total	5.4	[1]
Liabilities Recognized at Jun. 30, 2012	1.2	[1]
Other Subsidiaries [Member] | Guarantees: Fuel Purchase Related [Member]
Product Liability Contingency [Line Items]
2012	0	[1]
2013-2016	10.0	[1]
After 2016	95.3	[1],[2]
Total	105.3	[1]
Liabilities Recognized at Jun. 30, 2012	2.8	[1]
Energy Consolidated And Other Subsidiaries [Member]
Product Liability Contingency [Line Items]
2012	0
2013-2016	10.0
After 2016	100.7	[2]
Total	110.7
Liabilities Recognized at Jun. 30, 2012	$ 4.0

[1] The amounts shown are the maximum theoretical amounts guaranteed under current agreements. Liabilities recognized represent the associated obligation of TECO Energy under these agreements at June 30, 2012. The obligations under these letters of credit and guarantees include net accounts payable and net derivative liabilities.

[2] These letters of credit and guarantees renew annually and are shown on the basis that they will continue to renew beyond 2016.

[3] The amounts shown are the maximum theoretical amounts guaranteed under current agreements. Liabilities recognized represent the associated obligation of TEC under these agreements at June 30, 2012. The obligations under these letters of credit include net accounts payable and net derivative liabilities.

[4] These letters of credit renew annually and are shown on the basis that they will continue to renew beyond 2016.