Regulatory - Schedule of Regulatory Assets and Regulatory Liabilities (Parenthetical) (Detail)	6 Months Ended
Jun. 30, 2015
Schedule Of Regulatory Assets And Liabilities [Line Items]
Amortization period	5 years
Tampa Electric Company [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Amortization period	5 years

Amortization period for the recovery of regulatory liability, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_RegulatoryLiabilityAmortizationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration