Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended			56 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Equity method investment information	In certain circumstances this can result in the company consolidating entities in which it has less than a 50% equity investment and deconsolidating entities in which it has a majority equity interest
Equity method investment, Ownership percentage	50.00%			50.00%
Restricted cash	$ 0	$ 8.7		$ 0
Percentage of original cost of depreciable property	3.70%	3.80%	3.60%
Depreciation expense	316.5	309.3	306.6
Purchased power	64.7	105.3	125.9
Franchise fees and gross receipts taxes	108.5	111.5	109.3
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Discount rates used in estimating other self-insurance liabilities	3.51%	2.60%
Minimum [Member] | Computer Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period	2 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Discount rates used in estimating other self-insurance liabilities	4.86%	4.00%
Maximum [Member] | Computer Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period	15 years
Unbilled Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Unbilled revenues	46.7	49.0		46.7
Tampa Electric Company [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method investment information	In certain circumstances this can result in TEC consolidating entities in which it has less than a 50% equity investment and deconsolidating entities in which it has a majority equity interest
Equity method investment, Ownership percentage	50.00%			50.00%
Percentage of original cost of depreciable property	3.70%	3.80%	3.60%
Depreciation expense	284.2	275.1	263.7
Allowance for funds used during construction rate				8.16%
Allowance for funds used during construction	9.9	4.1	1.6
Purchased power	64.7	105.3	125.9
Franchise fees and gross receipts taxes	108.5	111.5	109.3
Tampa Electric Company [Member] | Computer Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period	15 years
Tampa Electric Company [Member] | Unbilled Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Unbilled revenues	46.7	49.0		46.7
TECO Energy Source [Member]
Summary Of Significant Accounting Policies [Line Items]
Costs netted against revenues	23.1	13.8	2.5
TECO Coal [Member]
Summary Of Significant Accounting Policies [Line Items]
Shipping and Handling	$ 8.2	$ 9.0	$ 16.6