ACQUISITIONS AND DISPOSITIONS - Southern Power Narrative (Details) $ in Millions	1 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($)	Jun. 30, 2019 USD ($) MW	Dec. 31, 2022	Dec. 31, 2021 USD ($) MW	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	May 31, 2019 MW
Asset Acquisition [Line Items]
Construction work in progress				$ 8,771	$ 8,697
Gain (loss) on dispositions				176	66	$ 2,588
Southern Power
Asset Acquisition [Line Items]
Construction work in progress				45	127
Gain (loss) on dispositions				$ 41	$ 39	24
Southern Power | Garland
Asset Acquisition [Line Items]
Nameplate capacity placed in service (in MWs) | MW				73
Southern Power | Tranquility Solar Storage
Asset Acquisition [Line Items]
Nameplate capacity placed in service (in MWs) | MW				32
Southern Power | Series of Business Acquisitions
Asset Acquisition [Line Items]
Construction costs incurred to date				$ 383
Southern Power | Minimum | Series of Business Acquisitions
Asset Acquisition [Line Items]
Aggregate construction costs				230
Southern Power | Maximum | Series of Business Acquisitions
Asset Acquisition [Line Items]
Aggregate construction costs				$ 270
Wind Generating Facility | Southern Power
Asset Acquisition [Line Items]
Project qualification for production tax credits, percentage				100.00%
Gain (loss) on dispositions				$ 37		$ 17
Gain (loss) on dispositions, after tax				$ 28
Scenario, Forecast | Wind Generating Facility | Southern Power
Asset Acquisition [Line Items]
Project qualification for production tax credits, percentage			80.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Nacogdoches Biomass-Fueled Facility | Southern Power
Asset Acquisition [Line Items]
Gain (loss) on dispositions		$ 23
Approximate nameplate capacity (in MWs) | MW		115
Consideration for sale		$ 461
Gain (loss) on dispositions, after tax		$ 88
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Mankato | Southern Power
Asset Acquisition [Line Items]
Gain (loss) on dispositions	$ 39
Approximate nameplate capacity (in MWs) | MW							385
Consideration for sale	663
Gain (loss) on dispositions, after tax	$ 23