Employee Postretirement Benefits - Schedule of One-percentage-point Change in Assumed Health Care Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Effect on periodic cost - Increase	$ 0.3
Effect on periodic cost - Decrease	(0.3)
Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on periodic cost - Increase	0.2
Effect on periodic cost - Decrease	(0.2)
Assumed One-percentage-point Change [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on postretirement benefit obligation - Increase	6.8
Effect on postretirement benefit obligation - Decrease	(6.1)
Assumed One-percentage-point Change [Member] \| Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on postretirement benefit obligation - Increase	5.6
Effect on postretirement benefit obligation - Decrease	$ (5.0)

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Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (m)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

+ Details

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- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

+ Details

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

+ Details

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

+ Details

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