Financing - Schedule of Long-Term Debt Financing Activities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Debt Instrument [Line Items]
Senior Note Maturities, Redemptions, and Repurchases	$ 2,300
Revenue Bond Issuances and Reofferings of Purchased Bonds	556
Revenue Bond Maturities, Redemptions, and Repurchases	248
Other Long-Term Debt Issuances	835
Other Long-Term Debt Redemptions and Maturities	12
Southern Company
Debt Instrument [Line Items]
Senior Note Maturities, Redemptions, and Repurchases	2,100
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
ALABAMA POWER CO
Debt Instrument [Line Items]
Senior Note Maturities, Redemptions, and Repurchases	200
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
GEORGIA POWER CO
Debt Instrument [Line Items]
Senior Note Maturities, Redemptions, and Repurchases	0
Revenue Bond Issuances and Reofferings of Purchased Bonds	513
Revenue Bond Maturities, Redemptions, and Repurchases	223
Other Long-Term Debt Issuances	835
Other Long-Term Debt Redemptions and Maturities	3
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Senior Note Maturities, Redemptions, and Repurchases	0
Revenue Bond Issuances and Reofferings of Purchased Bonds	43
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
Other
Debt Instrument [Line Items]
Senior Note Maturities, Redemptions, and Repurchases	0
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	25
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	$ 9