Earnings Per Share (Details) (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share [Abstract]
Net income	$ 90.3	$ 51.1	$ 219.6	$ 182.8
Less: Income attributable to noncontrolling interest	(0.1)	(0.1)	(0.2)	(0.5)
Less: Amount allocated to nonvested participating shareholders	(0.5)	(0.4)	(1.2)	(1.3)
Net income attributable to TECO Energy available to common shareholders - basic	89.7	50.6	218.2	181.0
Average shares outstanding common	213.8	212.8	213.5	212.5
Basic earnings per share attributable to TECO Energy available to common shareholders	$ 0.42	$ 0.24	$ 1.02	$ 0.85
Net income attributable to TECO Energy available to common shareholders - diluted	89.7	50.6	218.2	181.0
Assumed conversions of stock options, unvested restricted stock and contingent performance shares, net	$ 1.5	$ 2.3	$ 1.6	$ 2.1
Adjusted average shares outstanding common - diluted	215.3	215.1	215.1	214.6
Earnings per share - Diluted	$ 0.42	$ 0.24	$ 1.02	$ 0.85
Anti-dilutive shares	1.4	2.5	1.8	4.3