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Regulatory Assets and Liabilities (ROE of Tampa Electric) (Details) - Tampa Electric Division [Member]	12 Months Ended
	Dec. 31, 2018
Florida Public Service Commission [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Equity Capital Structure, Percentage	54.00%
Minimum [Member] | Florida Public Service Commission [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage	9.25%
Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage	10.25%
Maximum [Member] | Florida Public Service Commission [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage	11.25%

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Percentage of public utility's approved equity to capital, including debt and equity.

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Percentage of public utility's approved return on equity.

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