Segment and Related Information - Financial Data for Business Segments (Details) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Financial data for business segments
Operating revenues	$ 3,897,000,000		$ 3,604,000,000
Segment net income (loss)	81,000,000	[1],[2]	368,000,000	[1]
Total assets	63,274,000,000				63,149,000,000
After Tax Charge To Income	16,000,000
Electric Utilities [Member]
Financial data for business segments
Operating revenues	3,885,000,000		3,589,000,000
Segment net income (loss)	95,000,000	[1],[2]	369,000,000	[1]
Total assets	62,501,000,000				62,251,000,000
Traditional Operating Companies [Member] | Electric Utilities [Member]
Financial data for business segments
Operating revenues	3,668,000,000		3,449,000,000
Segment net income (loss)	66,000,000	[1],[2]	339,000,000	[1]
Total assets	58,752,000,000				58,600,000,000
Southern Power [Member]
Segment and Related Information (Textual) [Abstract]
Southern Power's revenues from sales to the traditional operating companies	78,000,000		112,000,000
Southern Power [Member] | Electric Utilities [Member]
Financial data for business segments
Operating revenues	303,000,000		254,000,000
Segment net income (loss)	29,000,000	[1],[2]	29,000,000	[1]
Total assets	3,858,000,000				3,780,000,000
Eliminations [Member]
Financial data for business segments
Operating revenues	(23,000,000)		(23,000,000)
Segment net income (loss)	2,000,000	[1],[2]	(3,000,000)	[1]
Total assets	(302,000,000)				(218,000,000)
Eliminations [Member] | Electric Utilities [Member]
Financial data for business segments
Operating revenues	(86,000,000)		(114,000,000)
Segment net income (loss)	0	[1],[2]	1,000,000	[1]
Total assets	(109,000,000)				(129,000,000)
All Other [Member]
Financial data for business segments
Operating revenues	35,000,000		38,000,000
Segment net income (loss)	(16,000,000)	[1],[2]	2,000,000	[1]
Total assets	1,075,000,000				1,116,000,000
Kemper Igcc [Member]
Segment Reporting Information [Line Items]
Pre-Tax Charge Of Income	540,000,000
Financial data for business segments
After Tax Charge To Income	$ 333,500,000

[1] After dividends on preferred and preference stock of subsidiaries

[2] Segment net income (loss) for the three months ended March 31, 2013 includes a $540.0 million pre-tax charge ($333.5 million after tax) for an estimated probable loss on the Kemper IGCC. See Note (B) under "Integrated Coal Gasification Combined Cycle" herein for additional information.