Other Comprehensive Income - Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Other Comprehensive Income Loss [Line Items]
Unrealized gain (loss) on cash flow hedges, Gross	$ 0.1	$ (0.7)	$ 0	$ (0.4)
Reclassification from AOCI to net income, Gross	0.1	0.5	0.5	0.8
Gain (Loss) on cash flow hedges, Gross	0.2	(0.2)	0.5	0.4
Amortization of unrecognized benefit costs, Gross	0.8	1.1	1.6	2.2
Increase in unrecognized post employment costs, Gross	0		(12.9)
Total other comprehensive income (loss), Gross	1.0	0.9	(10.8)	2.6
Unrealized gain (loss) on cash flow hedges, Tax	0	0.3	0	0.2
Reclassification from AOCI to net income, Tax	(0.1)	(0.2)	(0.2)	(0.3)
Gain (loss) on cash flow hedges, Tax	(0.1)	0.1	(0.2)	(0.1)
Amortization of unrecognized benefit costs, Tax	(0.3)	(0.4)	(0.6)	(0.8)
Increase in unrecognized post employment costs, Tax	0		4.7
Total other comprehensive income (loss), Tax	(0.4)	(0.3)	3.9	(0.9)
Unrealized gain (loss) on cash flow hedges, Net	0.1	(0.4)	0	(0.2)
Reclassification from AOCI to net income, Net	0	0.3	0.3	0.5
Gain (loss) on cash flow hedges, Net	0.1	(0.1)	0.3	0.3
Amortization of unrecognized benefit costs, Net	0.5	0.7	1.0	1.4
Increase in unrecognized post employment costs, Net	0	0	(8.2)	0
Total other comprehensive income (loss), Net	0.6	0.6	(6.9)	1.7
Tampa Electric Company [Member]
Other Comprehensive Income Loss [Line Items]
Unrealized gain (loss) on cash flow hedges, Gross		0		0
Reclassification from AOCI to net income, Gross		0.4		0.7
Gain (Loss) on cash flow hedges, Gross		0.4		0.7
Total other comprehensive income (loss), Gross		0.4		0.7
Unrealized gain (loss) on cash flow hedges, Tax	0	0	0	0
Reclassification from AOCI to net income, Tax	0	(0.2)	(0.2)	(0.3)
Gain (loss) on cash flow hedges, Tax	0	(0.2)	(0.2)	(0.3)
Total other comprehensive income (loss), Tax	0	(0.2)	(0.2)	(0.3)
Unrealized gain (loss) on cash flow hedges, Net	0	0	0	0
Reclassification from AOCI to net income, Net	0	0.2	0.2	0.4
Gain (loss) on cash flow hedges, Net	0	0.2	0.2	0.4
Total other comprehensive income (loss), Net	$ 0	$ 0.2	$ 0.2	$ 0.4