Short-Term Debt (Narrative) (Detail) (Tampa Electric Co [Member], USD $) In Millions, unless otherwise specified	1 Months Ended		6 Months Ended
Feb. 17, 2012	Jun. 30, 2012	Jun. 30, 2012 Minimum [Member]	Jun. 30, 2012 Maximum [Member]
Line of Credit Facility [Line Items]
Commitment fees, basis points	60		12.5	30.0
Weighted-average interest rate		1.08%
Borrowing facility, accounts receivable	$ 150
Federal funds rate plus basis points	50,000,000

Description of the fees for amounts available, but unused under the credit facility.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration