Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

ACQUISITIONS AND DISPOSITIONS - Alabama Power Narrative (Details) - Alabama Power - Autauga Combined Cycle Acquisition - MW	Sep. 06, 2019	Sep. 01, 2020
Business Acquisition [Line Items]
Power sales agreement, remaining term	3 years
Scenario, Forecast
Business Acquisition [Line Items]
Approximate nameplate capacity (in MW)		885