Discontinued Operations - Components of Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) Income from discontinued operations	$ (0.2)	$ (27.4)	$ 0	$ (7.9)
(Benefit) Provision for income taxes	0.1	(18.7)	0	(24.6)
(Loss) Income from discontinued operations, net	(0.1)	(46.1)	0	(32.5)
Less: Income from discontinued operations attributable to noncontrolling interest	0	0.1	0	0.3
(Loss) Income from discontinued operations attributable to TECO Energy, net	(0.1)	(46.2)	0	(32.8)
TECO Guatemala [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	0	31.5	0	100.4
(Loss) Income from operations	(0.2)	3.8	0	23.3
(Loss) gain on assets sold, including transaction costs	0	(31.2)	0	(31.2)
(Loss) Income from discontinued operations	(0.2)	(27.4)	0	(7.9)
(Benefit) Provision for income taxes	(0.1)	18.7	0	24.6
(Loss) Income from discontinued operations, net	(0.1)	(46.1)	0	(32.5)
Less: Income from discontinued operations attributable to noncontrolling interest	0	0.1	0	0.3
(Loss) Income from discontinued operations attributable to TECO Energy, net	$ (0.1)	$ (46.2)	$ 0	$ (32.8)