Financing - Schedule of Long-Term Debt Financing Activities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Debt Instrument [Line Items]
Senior Note Issuances	$ 1,050
Senior Note Maturities and Redemptions	450
Revenue Bond Maturities Redemptions and Repurchases	4
Other Long-Term Debt Issuances	947
Other Long-Term Debt Redemptions and Maturities	434
Consolidation, Eliminations [Member]
Debt Instrument [Line Items]
Other Long-Term Debt Issuances	(200)
Alabama Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances	400
Senior Note Maturities and Redemptions	200
Revenue Bond Maturities Redemptions and Repurchases	0
Other Long-Term Debt Issuances	45
Other Long-Term Debt Redemptions and Maturities	0
Georgia Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances	650
Senior Note Maturities and Redemptions	250
Revenue Bond Maturities Redemptions and Repurchases	4
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	1
Mississippi Power [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	1,100
Other Long-Term Debt Redemptions and Maturities	426
Southern Power [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	2
Other Long-Term Debt Redemptions and Maturities	3
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	$ 4