Acquisitions and Dispositions - Southern Company Narrative (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended		12 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2019	Jul. 22, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Preliminary gain			$ 2,512	$ (35)
Goodwill impairment		$ 32	$ 32
Disposal Group, Disposed of by Sale, Not Discontinued Operations | GULF POWER CO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses, net of cash divested	$ 5,800
Amount of indebtedness assumed at closing	$ 1,300
Disposal Group, Held-for-sale, Not Discontinued Operations | PowerSecure Utility Infrastructure Services Unit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment		$ 32
Scenario, Forecast | Disposal Group, Disposed of by Sale, Not Discontinued Operations | GULF POWER CO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Preliminary gain					$ 2,500
Preliminary gain, net of tax					$ 1,300
Subsequent Event | Disposal Group, Disposed of by Sale, Not Discontinued Operations | PowerSecure Utility Infrastructure Services Unit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale price						$ 71