Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Receivables	$ 2,343	$ 2,630
Contract Assets	70	102
Contract Liabilities	58	32
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Receivables	629	520
Contract Assets	0	0
Contract Liabilities	10	12
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Receivables	807	721
Contract Assets	30	58
Contract Liabilities	26	7
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Receivables	93	100
Contract Assets	0	0
Contract Liabilities	7	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Receivables	119	118
Contract Assets	0	0
Contract Liabilities	1	11
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Receivables	550	952
Contract Assets	0	0
Contract Liabilities	$ 1	$ 2

For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant