Earnings Per Share - Schedule of Earnings Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic earnings per share
Net income from continuing operations	$ 62.9	$ 90.2	$ 155.7	$ 200.4
Amount allocated to nonvested participating shareholders	(0.2)	(0.3)	(0.5)	(0.7)
Income before discontinued operations available to common shareholders - Basic	62.7	89.9	155.2	199.7
(Loss) Income from discontinued operations attributable to TECO Energy, net	(0.1)	(46.2)	0	(32.8)
Amount allocated to nonvested participating shareholders	0	0.1	0	0.1
(Loss) Income from discontinued operations attributable to TECO Energy available to common shareholders - Basic	(0.1)	(46.1)	0	(32.7)
Net income attributable to TECO Energy	62.8	44.0	155.7	167.6
Amount allocated to nonvested participating shareholders	(0.2)	(0.2)	(0.5)	(0.6)
Net income attributable to TECO Energy available to common shareholders - Basic	62.6	43.8	155.2	167.0
Average common shares outstanding - Basic	215.2	214.5	214.9	214.2
Earnings per share from continuing operations available to common shareholders - Basic	$ 0.29	$ 0.42	$ 0.72	$ 0.93
Earnings per share from discontinued operations attributable to TECO Energy available to common shareholders - Basic	$ 0.00	$ (0.22)	$ 0.00	$ (0.15)
Earnings per share attributable to TECO Energy available to common shareholders - Basic	$ 0.29	$ 0.20	$ 0.72	$ 0.78
Diluted earnings per share
Net income from continuing operations	62.9	90.2	155.7	200.4
Amount allocated to nonvested participating shareholders	(0.2)	(0.3)	(0.5)	(0.7)
Income before discontinued operations available to common shareholders - Diluted	62.7	89.9	155.2	199.7
(Loss) Income from discontinued operations attributable to TECO Energy, net	(0.1)	(46.2)	0	(32.8)
Amount allocated to nonvested participating shareholders	0	0.1	0	0.1
(Loss) Income from discontinued operations attributable to TECO Energy available to common shareholders - Diluted	(0.1)	(46.1)	0	(32.7)
Net income attributable to TECO Energy	62.8	44.0	155.7	167.6
Amount allocated to nonvested participating shareholders	(0.2)	(0.2)	(0.5)	(0.6)
Net income attributable to TECO Energy available to common shareholders - Diluted	$ 62.6	$ 43.8	$ 155.2	$ 167.0
Unadjusted average common shares outstanding - Diluted	215.2	214.5	214.9	214.2
Assumed conversion of stock options, unvested restricted stock and contingent performance shares, net	0.4	0.9	0.5	1.1
Average common shares outstanding - Diluted	215.6	215.4	215.4	215.3
Earnings per share from continuing operations available to common shareholders - Diluted	$ 0.29	$ 0.42	$ 0.72	$ 0.93
Earnings per share from discontinued operations attributable to TECO Energy available to common shareholders - Diluted	$ 0.00	$ (0.22)	$ 0.00	$ (0.15)
Earnings per share attributable to TECO Energy available to common shareholders - Diluted	$ 0.29	$ 0.20	$ 0.72	$ 0.78
Anti-dilutive shares	0	0	0	0.6