Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Name:	us-gaap_DeferredIncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2017
Effective Income Tax Computation [Line Items]
Federal statutory income tax rate		21.00%	21.00%	35.00%
Net operating losses carryback period	5 years
Percentage of deductibility of interest expense	50.00%
SCANA
Effective Income Tax Computation [Line Items]
Deferred income tax expense		$ 198