Fair Value Measurements (Schedule Of Recurring Fair Value Measures) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	$ 0.8	$ 0.9
Total Swap Liabilities	44.4	67.0
Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.5	0
Total Swap Liabilities	41.5	65.8
Natural Gas Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.5	0
Total Swap Liabilities	41.5	65.8
Natural Gas Derivatives [Member] | Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.5	0
Total Swap Liabilities	41.5	65.8
Diesel Fuel Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.3	0.9
Total Swap Liabilities	2.9	1.2
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Natural Gas Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Natural Gas Derivatives [Member] | Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Diesel Fuel Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.8	0.9
Total Swap Liabilities	44.4	67.0
Fair Value, Inputs, Level 2 [Member] | Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.5	0
Total Swap Liabilities	41.5	65.8
Fair Value, Inputs, Level 2 [Member] | Natural Gas Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.5	0
Total Swap Liabilities	41.5	65.8
Fair Value, Inputs, Level 2 [Member] | Natural Gas Derivatives [Member] | Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.5	0
Total Swap Liabilities	41.5	65.8
Fair Value, Inputs, Level 2 [Member] | Diesel Fuel Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0.3	0.9
Total Swap Liabilities	2.9	1.2
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Natural Gas Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Natural Gas Derivatives [Member] | Tampa Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Diesel Fuel Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	$ 0	$ 0