Short-Term Debt - Credit Facilities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Line Of Credit Facility [Line Items]
Credit Facilities	$ 900.0	$ 900.0
Borrowings Outstanding	206.0us-gaap_NotesPayableCurrent	139.0us-gaap_NotesPayableCurrent
Letters of Credit Outstanding	2.9	2.3
Tampa Electric Company [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	475.0	475.0
Borrowings Outstanding	47.0	58.0
Letters of Credit Outstanding	0.6	0.6
Tampa Electric Company [Member] \| 5-year Facility [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	325.0	325.0
Borrowings Outstanding	5.0	12.0
Letters of Credit Outstanding	0.6	0.6
Tampa Electric Company [Member] \| 1-year Accounts Receivable Facility [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	150.0	150.0
Borrowings Outstanding	42.0	46.0
Letters of Credit Outstanding	0	0
TECO Energy [Member] \| 5-year Facility [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	300.0	300.0
Borrowings Outstanding	144.0	50.0
Letters of Credit Outstanding	0	0
New Mexico Gas Company [Member] \| 5-year Facility [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	125.0	125.0
Borrowings Outstanding	15.0	31.0
Letters of Credit Outstanding	$ 2.3	$ 1.7

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sum of the carrying values as of the balance sheet date of the portions of long-term notes payable due within one year or the operating cycle if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19,20)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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