Employee Postretirement Benefits - Schedule of Amount Recognized in Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	$ 139.6	$ 216.5
Accrued benefit costs and other current liabilities	(3.3)	(5.3)
Deferred credits and other liabilities	(69.7)	(180.6)
Net amount recognized at end of year	99.7	83.7
Pension Benefits [Member] | Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	139.6	216.5
Accrued benefit costs and other current liabilities	(0.9)	(0.9)
Deferred credits and other liabilities	(50.1)	(139.8)
Net amount recognized at end of year	88.6	75.8
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	43.2	59.6
Accrued benefit costs and other current liabilities	(13.3)	(13.1)
Deferred credits and other liabilities	(194.8)	(217.2)
Net amount recognized at end of year	(189.1)	(188.6)
Other Postretirement Benefits [Member] | Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	43.2	59.6
Accrued benefit costs and other current liabilities	(10.8)	(10.6)
Deferred credits and other liabilities	(158.3)	(174.2)
Net amount recognized at end of year	$ (125.9)	$ (125.2)