Earnings Per Share - Schedule of Earnings Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic earnings per share
Net income from continuing operations	$ 45.6	$ 90.2	$ 65.6	$ 44.6	$ 47.3	$ 86.1	$ 72.0	$ 45.4	$ 246.0	$ 250.8	$ 211.6
Amount allocated to nonvested participating shareholders									(0.8)	(1.3)	(1.5)
Income before discontinued operations available to common shareholders - Basic									245.2	249.5	210.1
Income (loss) from discontinued operations attributable to TECO Energy, net									(33.3)	21.8	27.4
Amount allocated to nonvested participating shareholders									0.1	(0.1)	(0.2)
Income (loss) from discontinued operations attributable to TECO Energy available to common shareholders - Basic									(33.2)	21.7	27.2
Net income attributable to TECO Energy	45.1	44.0	73.1	50.5	53.2	90.2	77.5	51.7	212.7	272.6	239.0
Amount allocated to nonvested participating shareholders									(0.7)	(1.4)	(1.7)
Net income attributable to TECO Energy available to common shareholders - Basic									212.0	271.2	237.3
Average common shares outstanding - Basic									214.3	213.6	212.6
Earnings per share from continuing operations available to common shareholders - Basic	$ 0.21	$ 0.42	$ 0.30	$ 0.21	$ 0.22	$ 0.40	$ 0.34	$ 0.21	$ 1.14	$ 1.17	$ 0.99
Earnings per share from discontinued operations attributable to TECO Energy available to common shareholders - Basic									$ (0.15)	$ 0.10	$ 0.13
Earnings per share attributable to TECO Energy available to common shareholders - Basic									$ 0.99	$ 1.27	$ 1.12
Diluted earnings per share
Net income from continuing operations	45.6	90.2	65.6	44.6	47.3	86.1	72.0	45.4	246.0	250.8	211.6
Amount allocated to nonvested participating shareholders									(0.8)	(1.3)	(1.5)
Income before discontinued operations available to common shareholders - Diluted									245.2	249.5	210.1
Income (loss) from discontinued operations attributable to TECO Energy, net									(33.3)	21.8	27.4
Amount allocated to nonvested participating shareholders									0.1	(0.1)	(0.2)
Income (loss) from discontinued operations attributable to TECO Energy available to common shareholders - Diluted									(33.2)	21.7	27.2
Net income attributable to TECO Energy	45.1	44.0	73.1	50.5	53.2	90.2	77.5	51.7	212.7	272.6	239.0
Amount allocated to nonvested participating shareholders									(0.7)	(1.4)	(1.7)
Net income attributable to TECO Energy available to common shareholders - Diluted									212.0	271.2	237.3
Unadjusted average common shares outstanding - Diluted									214.3	213.6	212.6
Assumed conversion of stock options, unvested restricted stock and contingent performance shares, net									$ 0.7	$ 1.5	$ 2.2
Average common shares outstanding - Diluted									215.0	215.1	214.8
Earnings per share from continuing operations available to common shareholders - Diluted	$ 0.21	$ 0.42	$ 0.30	$ 0.20	$ 0.22	$ 0.40	$ 0.34	$ 0.21	$ 1.14	$ 1.17	$ 0.98
Earnings per share from discontinued operations attributable to TECO Energy available to common shareholders - Diluted									$ (0.15)	$ 0.10	$ 0.13
Earnings per share attributable to TECO Energy available to common shareholders - Diluted									$ 0.99	$ 1.27	$ 1.11
Anti-dilutive shares									0.4	1.7	2.7