Discontinued Operations - Components of Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations	$ (10.6)	$ 33.3	$ 88.4
Income (loss) from discontinued operations, net	(33.0)	22.1	28.0
Less: Income from discontinued operations attributable to noncontrolling interest	0.3	0.3	0.6
Income (loss) from discontinued operations attributable to TECO Energy, net	(33.3)	21.8	27.4
TECO Guatemala [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	114.2	133.5	124.4
Income from operations	27.7	33.7	88.4
Loss on assets sold and held for sale, including transaction costs	(38.3)	(0.4)	0
Income (loss) from discontinued operations	(10.6)	33.3	88.4
Provision for income taxes	22.4	11.2	60.4
Income (loss) from discontinued operations, net	(33.0)	22.1	28.0
Less: Income from discontinued operations attributable to noncontrolling interest	0.3	0.3	0.6
Income (loss) from discontinued operations attributable to TECO Energy, net	$ (29.3)	$ 22.4	$ 41.6