Income Taxes (Details)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	8.40%	16.20%
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	(17.30%)	13.50%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration