ACQUISITIONS AND DISPOSITIONS - Southern Power Narrative (Details) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2020 USD ($)	Dec. 31, 2022 USD ($) MW	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 MW
Asset Acquisition [Line Items]
Construction work in progress		$ 10,896	$ 8,771
Gain (loss) on dispositions		42	176	$ 66
Southern Power
Asset Acquisition [Line Items]
Construction work in progress		41	45
Gain (loss) on dispositions		$ 2	$ 41	$ 39
Southern Power | Garland
Asset Acquisition [Line Items]
Nameplate capacity placed in service (in MWs) | MW		15
Southern Power | Tranquility Solar Storage
Asset Acquisition [Line Items]
Nameplate capacity placed in service (in MWs) | MW		40
Wind Generating Facility | Southern Power
Asset Acquisition [Line Items]
Gain (loss) on dispositions		$ 37
Gain (loss) on dispositions, after tax		$ 28
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