Employee Postretirement Benefits - Schedule of Funded Status (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 593,000,000	$ 529,100,000
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	593,000,000	529,100,000	467,600,000
Less: Benefit obligation (PBO/APBO)	666,000,000	715,000,000	646,400,000
Funded status at end of year	(73,000,000)	(185,900,000)
Unrecognized net actuarial loss	173,100,000	270,300,000
Unrecognized prior service (benefit) cost	(400,000)	(700,000)
Net amount required to be recognized at end of year	99,700,000	83,700,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0	0
Less: Benefit obligation (PBO/APBO)	208,100,000	230,300,000	216,500,000
Funded status at end of year	(208,100,000)	(230,300,000)
Unrecognized net actuarial loss	19,700,000	42,700,000
Unrecognized prior service (benefit) cost	(700,000)	(1,000,000)
Net amount required to be recognized at end of year	(189,100,000)	(188,600,000)
TECO Energy [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	593,000,000	529,100,000	467,600,000
Less: Benefit obligation (PBO/APBO)	666,000,000	715,000,000	646,400,000
Funded status at end of year	(73,000,000)	(185,900,000)
Unrecognized net actuarial loss	173,100,000	270,300,000
Unrecognized prior service (benefit) cost	(400,000)	(700,000)
Net amount required to be recognized at end of year	99,700,000	83,700,000
Unrecognized net transition obligation	0	0
TECO Energy [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0	0
Less: Benefit obligation (PBO/APBO)	208,100,000	230,300,000	216,500,000
Funded status at end of year	(208,100,000)	(230,300,000)
Unrecognized net actuarial loss	19,700,000	42,700,000
Unrecognized prior service (benefit) cost	(700,000)	(1,000,000)
Net amount required to be recognized at end of year	(189,100,000)	(188,600,000)
Unrecognized net transition obligation	$ 0	$ 0