Regulatory - Regulatory Assets and Related Recovery Periods (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Regulatory Assets [Line Items]
Regulatory assets	$ 327.4	$ 452.9
Tampa Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory assets	327.4	452.9
Clause Recoverable [Member]
Regulatory Assets [Line Items]
Regulatory assets	10.2	47.0
Clause Recoverable [Member] | Tampa Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory assets	10.2	47.0
Components of Rate Base [Member]
Regulatory Assets [Line Items]
Regulatory assets	185.6	279.1
Components of Rate Base [Member] | Tampa Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory assets	185.6	279.1
Regulatory Tax Asset [Member]
Regulatory Assets [Line Items]
Regulatory assets	67.4	67.2
Regulatory Tax Asset [Member] | Tampa Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory assets	67.4	67.2
Capital Structure and Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	64.2	59.6
Capital Structure and Other [Member] | Tampa Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 64.2	$ 59.6