Financing - Schedule of Long-Term Debt Financing Activities (Details) - USD ($)	1 Months Ended	9 Months Ended
	May 31, 2016	Sep. 30, 2016
Debt Instrument [Line Items]
Senior Note Issuances		$ 11,981,000,000
Senior Note Maturities and Redemptions		1,825,000,000
Revenue Bond Maturities Redemptions and Repurchases		4,000,000
Other Long-Term Debt Issuances		2,110,000,000
Other Long-Term Debt Redemptions and Maturities		576,000,000
Consolidation, Eliminations [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		(200,000,000)
Other Long-Term Debt Redemptions and Maturities		(225,000,000)
Southern Company [Member]
Debt Instrument [Line Items]
Senior Note Issuances	$ 8,500,000,000.0	8,500,000,000
Senior Note Maturities and Redemptions		500,000,000
Revenue Bond Maturities Redemptions and Repurchases		0
Other Long-Term Debt Issuances		800,000,000
Other Long-Term Debt Redemptions and Maturities		0
Alabama Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances		400,000,000
Senior Note Maturities and Redemptions		200,000,000
Revenue Bond Maturities Redemptions and Repurchases		0
Other Long-Term Debt Issuances		45,000,000
Other Long-Term Debt Redemptions and Maturities		0
Georgia Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances		650,000,000
Senior Note Maturities and Redemptions		700,000,000
Revenue Bond Maturities Redemptions and Repurchases		4,000,000
Other Long-Term Debt Issuances		300,000,000
Other Long-Term Debt Redemptions and Maturities		5,000,000
Gulf Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances		0
Senior Note Maturities and Redemptions		125,000,000
Revenue Bond Maturities Redemptions and Repurchases		0
Other Long-Term Debt Issuances		2,000,000
Other Long-Term Debt Redemptions and Maturities		0
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		1,100,000,000
Other Long-Term Debt Redemptions and Maturities		652,000,000
Southern Power [Member]
Debt Instrument [Line Items]
Senior Note Issuances		1,531,000,000
Senior Note Maturities and Redemptions		0
Revenue Bond Maturities Redemptions and Repurchases		0
Other Long-Term Debt Issuances		63,000,000
Other Long-Term Debt Redemptions and Maturities		84,000,000
Southern Company Gas [Member]
Debt Instrument [Line Items]
Senior Note Issuances		900,000,000
Senior Note Maturities and Redemptions		300,000,000
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		$ 60,000,000