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Revenue from Contracts with Customers and Lease Income - Schedule of Contract Balances (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 3,083	$ 3,139
Contract Assets	338	294
Contract Liabilities	257	213
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	649	716
Contract Assets	5	3
Contract Liabilities	9	6
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	1,179	1,278
Contract Assets	196	160
Contract Liabilities	76	75
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	119	115
Contract Assets	0	0
Contract Liabilities	2	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	94	132
Contract Assets	0	0
Contract Liabilities	1	2
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Accounts Receivable	925	864
Contract Assets	67	67
Contract Liabilities	$ 0	$ 0

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Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

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