Financing - Schedule of Long-Term Debt Financing Activities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($)
Debt Instrument [Line Items]
Senior Note Issuances	$ 2,450
Senior Note Maturities and Redemptions	735
Revenue Bond Maturities, Redemptions, and Repurchases	27
Other Long-Term Debt Issuances	509
Other Long-Term Debt Redemptions and Maturities	716
Southern Company
Debt Instrument [Line Items]
Senior Note Issuances	300
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	500
Other Long-Term Debt Redemptions and Maturities	400
ALABAMA POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	550
Senior Note Maturities and Redemptions	200
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 Issuances	850
Senior Note Maturities and Redemptions	450
Revenue Bond Maturities, Redemptions, and Repurchases	27
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	3
GULF POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	300
Senior Note Maturities and Redemptions	85
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	6
Other Long-Term Debt Redemptions and Maturities	0
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	40
Other Long-Term Debt Redemptions and Maturities	893
SOUTHERN POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	3
Other Long-Term Debt Redemptions and Maturities	3
SOUTHERN Co GAS
Debt Instrument [Line Items]
Senior Note Issuances	450
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
Other [Member]
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	8
Consolidation Eliminations
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	(40)
Other Long-Term Debt Redemptions and Maturities	$ (591)