Employee Postretirement Benefits - Schedule of Change in Plan Assets (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Change in plan assets
Fair value of plan assets at beginning of year	$ 529,100,000
Employer contributions	42,000,000	35,500,000
Fair value of plan assets at end of year	593,000,000	529,100,000
Pension Benefits [Member]
Change in plan assets
Fair value of plan assets at beginning of year	529,100,000	467,600,000
Actual return on plan assets	63,700,000	57,900,000
Employer contributions	45,900,000	36,800,000
Plan participants' contributions	0	0
Settlements	(2,600,000)	0
Gross benefits paid	(43,100,000)	(33,200,000)
Fair value of plan assets at end of year	593,000,000	529,100,000
Other Postretirement Benefits [Member]
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	11,900,000	9,800,000
Plan participants' contributions	2,900,000	3,700,000
Settlements	0	0
Gross benefits paid	(14,800,000)	(13,500,000)
Fair value of plan assets at end of year	0	0
TECO Energy [Member] | Pension Benefits [Member]
Change in plan assets
Fair value of plan assets at beginning of year	529,100,000	467,600,000
Actual return on plan assets	63,700,000	57,900,000
Employer contributions	45,900,000	36,800,000
Plan participants' contributions	0	0
Settlements	(2,600,000)	0
Gross benefits paid	(43,100,000)	(33,200,000)
Fair value of plan assets at end of year	593,000,000	529,100,000
TECO Energy [Member] | Other Postretirement Benefits [Member]
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	11,900,000	9,800,000
Plan participants' contributions	2,900,000	3,700,000
Settlements	0	0
Gross benefits paid	(14,800,000)	(13,500,000)
Fair value of plan assets at end of year	$ 0	$ 0