Effective income tax rate reconciliation assets expensing.

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Income taxes.

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Increase decrease in deferred income taxes offset to regulatory liability.

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Current regulatory liabilities generally represent obligations to make refunds to customers for various reasons including overpayment.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of unrecognized tax benefits.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Federal statutory tax rate			21.00%			35.00%
Asset expensing			100.00%
Provision for income taxes	$ 23	$ 31	$ 63	$ 65
Unrecognized tax benefits	8		8		$ 8
Unrecognized tax benefit that would reduce effective tax rate	8		$ 8		$ 8
Tampa Electric [Member]
Income Taxes [Line Items]
Effective tax rate			17.50%	19.60%
Florida [Member]
Income Taxes [Line Items]
Federal statutory tax rate			4.458%		5.50%
Provision for income taxes			$ (3)
Customer refund liability	$ 2		2
Decrease in deferred income taxes offset to regulatory liability			$ 5