Property, Plant, and Equipment - Ownership and Investment in Jointly-Owned Facilities (Details) $ in Millions	1 Months Ended
Aug. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) mi
Alabama Power
Other Ownership Interests [Line Items]
Percent Ownership		14.00%
Alabama Power \| Greene County (natural gas) Units 1 and 2
Other Ownership Interests [Line Items]
Percent Ownership		60.00%
Plant in Service		$ 274
Accumulated Depreciation		71
CWIP		$ 1
Alabama Power \| Plant Miller (coal) Units 1 and 2
Other Ownership Interests [Line Items]
Percent Ownership		91.80%
Plant in Service		$ 2,056
Accumulated Depreciation		619
CWIP		$ 138
Georgia Power \| Plant Hatch (nuclear)
Other Ownership Interests [Line Items]
Percent Ownership		50.10%
Plant in Service		$ 1,569
Accumulated Depreciation		615
CWIP		$ 54
Georgia Power \| Plant Vogtle (nuclear) Units 1 and 2
Other Ownership Interests [Line Items]
Percent Ownership		45.70%
Plant in Service		$ 3,804
Accumulated Depreciation		2,150
CWIP		$ 84
Georgia Power \| Plant Scherer (coal) Units 1 and 2
Other Ownership Interests [Line Items]
Percent Ownership		8.40%
Plant in Service		$ 266
Accumulated Depreciation		96
CWIP		$ 14
Georgia Power \| Plant Scherer (coal) Unit 3
Other Ownership Interests [Line Items]
Percent Ownership		75.00%
Plant in Service		$ 1,238
Accumulated Depreciation		493
CWIP		$ 66
Georgia Power \| Plant Wansley (coal)
Other Ownership Interests [Line Items]
Percent Ownership		53.50%
Plant in Service		$ 1,179
Accumulated Depreciation		362
CWIP		$ 160
Georgia Power \| Rocky Mountain (pumped storage)
Other Ownership Interests [Line Items]
Percent Ownership		25.40%
Plant in Service		$ 184
Accumulated Depreciation		135
CWIP		$ 0
Mississippi Power \| Plant Daniel (coal) Units 1 and 2
Other Ownership Interests [Line Items]
Percent Ownership		50.00%
Plant in Service		$ 723
Accumulated Depreciation		201
CWIP		$ 7
Southern Company Gas \| Dalton Pipeline (natural gas pipeline)
Other Ownership Interests [Line Items]
Percent Ownership		50.00%
Plant in Service		$ 270
Accumulated Depreciation		6
CWIP		$ 0
Pipeline infrastructure (miles) \| mi		115
Agreement to lease undivided ownership (percent)	50.00%
Future minimum payments receivable	$ 26
Initial term of contract	25 years
Alabama Power \| Mississippi Power \| Greene County (natural gas) Units 1 and 2
Other Ownership Interests [Line Items]
Percent Ownership		40.00%
Plant in Service		$ 180
Accumulated Depreciation		93
CWIP		$ 1

Pipeline Infrastructure

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- Definition

Undivided Ownership Interest To Be Leased

+ References

No definition available.

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- Definition

The period end amount owned by the reporting utility of a jointly owned utility plant in service.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.C)
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- Definition

The period end amount of construction work in progress at a jointly owned electricity generation plant.

+ References

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+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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