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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic earnings per share
Net income from continuing operations	$ 42.1	$ 62.9	$ 51.6	$ 41.2	$ 45.6	$ 90.2	$ 65.6	$ 44.6	$ 197.8	$ 246.0	$ 250.8
Amount allocated to nonvested participating shareholders									(0.6)	(0.8)	(1.3)
Income before discontinued operations available to common shareholders - Basic									197.2	245.2	249.5
Income (loss) from discontinued operations attributable to TECO Energy, net									(0.1)	(33.3)	21.8
Amount allocated to nonvested participating shareholders									0	0.1	(0.1)
Income (loss) from discontinued operations attributable to TECO Energy available to common shareholders - Basic									(0.1)	(33.2)	21.7
Net income attributable to TECO Energy	42.0	62.8	51.4	41.5	45.1	44.0	73.1	50.5	197.7	212.7	272.6
Amount allocated to nonvested participating shareholders									(0.6)	(0.7)	(1.4)
Net income attributable to TECO Energy available to common shareholders - Basic									197.1	212.0	271.2
Average common shares outstanding - Basic									215.0	214.3	213.6
Earnings per share from continuing operations available to common shareholders - Basic	$ 0.20	$ 0.29	$ 0.24	$ 0.19	$ 0.21	$ 0.42	$ 0.30	$ 0.21	$ 0.92	$ 1.14	$ 1.17
Earnings per share from discontinued operations attributable to TECO Energy available to common shareholders - Basic									$ 0.00	$ (0.15)	$ 0.10
Earnings per share attributable to TECO Energy available to common shareholders - Basic									$ 0.92	$ 0.99	$ 1.27
Diluted earnings per share
Net income from continuing operations	42.1	62.9	51.6	41.2	45.6	90.2	65.6	44.6	197.8	246.0	250.8
Amount allocated to nonvested participating shareholders									(0.6)	(0.8)	(1.3)
Income before discontinued operations available to common shareholders - Diluted									197.2	245.2	249.5
Income (loss) from discontinued operations attributable to TECO Energy, net									(0.1)	(33.3)	21.8
Amount allocated to nonvested participating shareholders									0	0.1	(0.1)
Income (loss) from discontinued operations attributable to TECO Energy available to common shareholders - Diluted									(0.1)	(33.2)	21.7
Net income attributable to TECO Energy	42.0	62.8	51.4	41.5	45.1	44.0	73.1	50.5	197.7	212.7	272.6
Amount allocated to nonvested participating shareholders									(0.6)	(0.7)	(1.4)
Net income attributable to TECO Energy available to common shareholders - Diluted									$ 197.1	$ 212.0	$ 271.2
Unadjusted average common shares outstanding - Diluted									215.0	214.3	213.6
Assumed conversion of stock options, unvested restricted stock and contingent performance shares, net									0.5	0.7	1.5
Average common shares outstanding - Diluted									215.5	215.0	215.1
Earnings per share from continuing operations available to common shareholders - Diluted	$ 0.20	$ 0.29	$ 0.24	$ 0.19	$ 0.21	$ 0.42	$ 0.30	$ 0.20	$ 0.92	$ 1.14	$ 1.17
Earnings per share from discontinued operations attributable to TECO Energy available to common shareholders - Diluted									$ 0.00	$ (0.15)	$ 0.10
Earnings per share attributable to TECO Energy available to common shareholders - Diluted									$ 0.92	$ 0.99	$ 1.27
Anti-dilutive shares									0	0.4	1.7