Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Qualifying hedges:
Changes in fair value, tax	$ (10)	$ (30)
Reclassification adjustment for amounts included in net income, tax	18	13
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	1	2
ALABAMA POWER CO
Qualifying hedges:
Reclassification adjustment for amounts included in net income, tax	0	0
GEORGIA POWER CO
Qualifying hedges:
Changes in fair value, tax	0	(1)
Reclassification adjustment for amounts included in net income, tax	0	1
SOUTHERN POWER CO
Qualifying hedges:
Changes in fair value, tax	(11)	(21)
Reclassification adjustment for amounts included in net income, tax	15	10
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	0	0
SOUTHERN Co GAS
Qualifying hedges:
Changes in fair value, tax	0	(7)
Reclassification adjustment for amounts included in net income, tax	$ 1	$ 2

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Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e640-108580

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Amount of tax expense (benefit) for reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
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