Regulatory - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Jan. 25, 2011	Dec. 31, 2010	Dec. 31, 2011
Period of average base rate	13 months
Revenue due to average base rate	$ 3,400,000,000
Increase in revenue by modification in base rate	33,500,000
Expected revenue requirement	135,000,000
Annual accrual storm damage reserve	8,000,000
Storm damage reserve	50,400,000			43,600,000
Stipulation earnings		11.75%	11.75%
One time reduction to customers bills		3,000,000
Minimum [Member]
Percentage of return on equity	11.25%
Maximum [Member]
Higher Revenue Requirements	104,000,000
TAMPA ELECTRIC CO [Member]
Percentage of capital structure equity	54.00%
Period of average base rate	13 months
Revenue due to average base rate	3,400,000,000
Increase in revenue by modification in base rate	33,500,000
Expected revenue requirement	135,000,000
Annual accrual storm damage reserve	8,000,000
Storm damage reserve	50,400,000			43,600,000
Stipulation earnings		11.75%	11.75%
One time reduction to customers bills		3,000,000
Remaining balance of customer reserve charged to accumulated depreciation reserves	6,200,000
TAMPA ELECTRIC CO [Member] | Minimum [Member]
Percentage of return on equity	11.25%
TAMPA ELECTRIC CO [Member] | Maximum [Member]
Higher Revenue Requirements	$ 104,000,000