Financing - Schedule of Long-Term Debt Financing Activities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Debt Instrument [Line Items]
Senior Note Issuances	$ 1,400
Senior Note Maturities and Redemptions	200
Other Long-Term Debt Issuances	9
Other Long-Term Debt Redemptions and Maturities	408
Southern Company [Member]
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	400
Alabama Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances	550
Senior Note Maturities and Redemptions	200
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
Georgia Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances	850
Senior Note Maturities and Redemptions	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	2
Gulf Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Other Long-Term Debt Issuances	6
Other Long-Term Debt Redemptions and Maturities	0
Southern Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Other Long-Term Debt Issuances	3
Other Long-Term Debt Redemptions and Maturities	2
Other [Member]
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	$ 4