Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Income Tax Expense Benefit	$ 108.8	$ 160.2	$ 153.9
Cash paid for income taxes	1.8	7.2	9.4
Use of operating loss carryforward		13.6	32.1
Effective tax rate	35.00%	35.00%	35.00%
Federal and state (Florida) net operating losses (NOL's) carry forward	1,321.9
Deferred tax assets expiration date	2025 and 2028
General business credit	3.9
Deferred tax general business credits expiration date	2026 and 2032
Foreign tax credits	38.5
Tax credit carry forwards	213.0	211.8
Valuation allowance release	3.0
Tax benefits, likelihood of being realized upon ultimate settlement	50.00%
Interest charges associated with uncertain tax positions	(0.9)	0.3	0.2
Interest accrued	0	0.9
Penalties	0
Income tax examination period	1 year
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Federal and state (Florida) net operating losses (NOL's) carry forward	392.6
Capital loss carryforward valuation allowance		3.0
Minimum [Member]
Income Taxes [Line Items]
Effective tax rate	35.00%
Tax credit carry forwards	211.8
Statutes of limitations	3 years
Maximum [Member]
Income Taxes [Line Items]
Tax credit carry forwards	213.0
Statutes of limitations	4 years
Tampa Electric Company [Member]
Income Taxes [Line Items]
Cash paid for income taxes	$ 56.4	$ (9.7)	$ (31.1)
Effective tax rate	35.00%	35.00%	35.00%
Tax benefits, likelihood of being realized upon ultimate settlement	50.00%
Statutes of limitations	3 years
Income tax examination period	1 year