Financing - Schedule of Long-Term Debt Financing Activities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Debt Instrument [Line Items]
Senior Note Issuances	$ 600
Revenue Bond Maturities, Redemptions, and Repurchases	278
Other Long-Term Debt Redemptions and Maturities	1,005
GEORGIA POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	0
Revenue Bond Maturities, Redemptions, and Repurchases	278
Other Long-Term Debt Redemptions and Maturities	102
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	600
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Redemptions and Maturities	900
Other
Debt Instrument [Line Items]
Senior Note Issuances	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Redemptions and Maturities	$ 3