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FINANCING - Notes Payable (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 1,440 | $ 609
Weighted Average Interest Rate | 0.40% | 0.30%
Commercial paper |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 1,140 | $ 609
Weighted Average Interest Rate | 0.30% | 0.30%
Short-term bank debt |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 300 | $ 0
Weighted Average Interest Rate | 0.70% | 0.00%
Georgia Power |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 0 | $ 60
Georgia Power | Commercial paper |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 0 | $ 60
Weighted Average Interest Rate | 0.00% | 0.30%
Mississippi Power |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 0 | $ 25
Mississippi Power | Commercial paper |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 0 | $ 25
Weighted Average Interest Rate | 0.00% | 0.40%
Southern Power |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 211 | $ 175
Southern Power | Commercial paper |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 211 | $ 175
Weighted Average Interest Rate | 0.30% | 0.30%
Southern Company Gas |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 1,209 | $ 324
Southern Company Gas | Commercial paper |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 1,209 | $ 324
Weighted Average Interest Rate | 0.40% | 0.20%
Southern Company Gas Capital | Commercial paper |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 379 | $ 220
Weighted Average Interest Rate | 0.30% | 0.30%
Nicor Gas | Commercial paper |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 530 | $ 104
Weighted Average Interest Rate | 0.30% | 0.20%
Nicor Gas | Short-term bank debt |  |
Short-term Debt [Line Items] |  |
Amount Outstanding | $ 300 | $ 0
Weighted Average Interest Rate | 0.70% | 0.00%

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