Accounting For Derivative Instruments And Hedging Activities (Fair Value Of The Overall Contractual Contingent Liability Positions) (Details) (USD $) In Millions	Sep. 30, 2011
Fair Value Asset/ (Liability)	$ (35.1)
Derivative Exposure Asset/ (Liability)	(35.1)
Posted Collateral	0
Tampa Electric Co [Member]
Fair Value Asset/ (Liability)	(34.0)
Derivative Exposure Asset/ (Liability)	(34.0)
Posted Collateral	$ 0

Fair value as of the balance sheet date of the assets less the liabilities of a derivative or group of derivatives.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13495-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611

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