Quarterly Data - Schedule of Financial Data by Quarter (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
Revenues	$ 688.4	$ 858.6	$ 752.5	$ 697.1	$ 720.0	$ 877.8	$ 849.5	$ 762.5	$ 2,996.6	$ 3,209.9	$ 3,363.5
Income from operations	109.5	183.1	149.1	114.8	120.8	181.3	160.3	120.7	556.5	583.2	581.0
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
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
EPS - Basic
From continuing operations	$ 0.21	$ 0.42	$ 0.30	$ 0.21	$ 0.22	$ 0.40	$ 0.34	$ 0.21	$ 1.14	$ 1.17	$ 0.99
Attributable to TECO Energy									$ 0.99	$ 1.27	$ 1.12
EPS - Diluted
From continuing operations	$ 0.21	$ 0.42	$ 0.30	$ 0.20	$ 0.22	$ 0.40	$ 0.34	$ 0.21	$ 1.14	$ 1.17	$ 0.98
Attributable to TECO Energy									$ 0.99	$ 1.27	$ 1.11
Dividends paid per common share outstanding	$ 0.220	$ 0.220	$ 0.220	$ 0.220	$ 0.215	$ 0.215	$ 0.215	$ 0.205	$ 0.880	$ 0.850	$ 0.815
TECO ENERGY, INC. [Member]
EPS - Basic
Attributable to TECO Energy	$ 0.21	$ 0.20	$ 0.34	$ 0.24	$ 0.25	$ 0.42	$ 0.36	$ 0.24
EPS - Diluted
Attributable to TECO Energy	$ 0.21	$ 0.20	$ 0.34	$ 0.23	$ 0.25	$ 0.42	$ 0.36	$ 0.24