Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred tax liabilities
Property related	$ 1,164.2	$ 1,023.3
Deferred fuel	1.6	11.3
Pension	52.8	43.0
Total deferred tax liabilities	1,218.6	1,077.6
Deferred tax assets
Alternative minimum tax credit carryforward	213.0	211.8
Loss and credit carryforwards	479.8	473.2
Other postretirement benefits	68.9	68.0
Other	113.2	113.0
Total deferred tax assets	874.9	866.0
Valuation allowance	0	(3.0)
Total deferred tax assets, net of valuation allowance	874.9	863.0
Total deferred tax liability, net	343.7	214.6
Less: Current portion of deferred tax asset	(100.3)	(63.3)
Long-term portion of deferred tax liability, net	444.0	277.9
Tampa Electric Company [Member]
Deferred tax liabilities
Property related	1,166.4	1,016.2
Deferred fuel	1.6	11.3
Pension	43.2	36.7
Total deferred tax liabilities	1,281.7	1,193.0
Pension and postretirement benefits	70.5	106.6
Other	0	22.2
Deferred tax assets
Other	4.4	0
Total deferred tax assets	196.8	232.1
Medical benefits	50.9	49.0
Insurance reserves	29.1	31.1
Investment tax credits	5.3	5.5
Hedging activities	4.9	5.5
Pension and postretirement benefits	70.5	106.6
Unbilled revenue	12.1	14.8
Capitalized energy conservation assistance costs	19.6	19.6
Total deferred tax liability, net	1,084.9	960.9
Less: Current portion of deferred tax asset	(29.4)	(20.0)
Long-term portion of deferred tax liability, net	$ 1,114.3	$ 980.9