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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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INTRODUCTION - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended		12 Months Ended
INTRODUCTION - Narrative (Details) $ in Millions	Jun. 30, 2020 USD ($) facility	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill	$ 5,280		$ 5,280		$ 5,280
SOUTHERN Co GAS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill	5,015		5,015		$ 5,015
Inventory decrement		$ 7		$ 10
ALABAMA POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Asset retirement obligation, period increase	$ 462
Number of facilities, closure designs completed \| facility	1
PowerSecure
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill	$ 263		$ 263
Maximum \| Natural Gas Generating Facility \| SOUTHERN POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life			50 years		45 years