Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value Assets Liabilities Measured On Recurring Basis [Line Items]
Total Swap Assets	$ 8.7	$ 10.0
Total Swap Liabilities	0.3	0.3
Fair Value, Measurements, Recurring [Member]
Fair Value Assets Liabilities Measured On Recurring Basis [Line Items]
Total Swap Assets	8.7	10.0
Total Swap Liabilities	0.3	0.3
Tampa Electric Company [Member]
Fair Value Assets Liabilities Measured On Recurring Basis [Line Items]
Total Swap Assets	8.6	9.8
Total Swap Liabilities	0.3	0.2
Tampa Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets Liabilities Measured On Recurring Basis [Line Items]
Total Swap Assets	8.6	9.8
Total Swap Liabilities	0.3	0.2
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets Liabilities Measured On Recurring Basis [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	0	0
Level 3 [Member] | Tampa Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets Liabilities Measured On Recurring Basis [Line Items]
Total Swap Assets	0	0
Total Swap Liabilities	$ 0	$ 0