Segment and Related Information - Financial Data for Business Segments (Details) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of States in which Entity Operates	4
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	$ 4,644,000,000		$ 3,897,000,000
Financial data for business segments
Electric Utilities' Revenues	4,644,000,000		3,897,000,000
Segment net income (loss)	351,000,000	[1],[2]	81,000,000	[1]
Total assets	64,838,000,000				64,546,000,000
Electric Utilities [Member]
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	4,627,000,000		3,885,000,000
Financial data for business segments
Electric Utilities' Revenues	4,627,000,000		3,885,000,000
Segment net income (loss)	351,000,000	[1],[2]	95,000,000	[1]
Total assets	64,160,000,000				63,775,000,000
Traditional Operating Companies [Member] | Electric Utilities [Member]
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	4,378,000,000		3,668,000,000
Financial data for business segments
Electric Utilities' Revenues	4,378,000,000		3,668,000,000
Segment net income (loss)	318,000,000	[1],[2]	66,000,000	[1]
Total assets	59,854,000,000				59,447,000,000
Southern Power [Member]
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	72,000,000		78,000,000
Financial data for business segments
Electric Utilities' Revenues	72,000,000		78,000,000
Southern Power [Member] | Electric Utilities [Member]
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	351,000,000		303,000,000
Financial data for business segments
Electric Utilities' Revenues	351,000,000		303,000,000
Segment net income (loss)	33,000,000	[1],[2]	29,000,000	[1]
Total assets	4,404,000,000				4,429,000,000
Eliminations [Member]
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	(24,000,000)		(23,000,000)
Financial data for business segments
Electric Utilities' Revenues	(24,000,000)		(23,000,000)
Segment net income (loss)	0	[1],[2]	2,000,000	[1]
Total assets	(415,000,000)				(306,000,000)
Eliminations [Member] | Electric Utilities [Member]
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	(102,000,000)		(86,000,000)
Financial data for business segments
Electric Utilities' Revenues	(102,000,000)		(86,000,000)
Segment net income (loss)	0	[1],[2]	0	[1]
Total assets	(98,000,000)				(101,000,000)
All Other [Member]
Segment and Related Information (Textual) [Abstract]
Electric Utilities' Revenues	41,000,000		35,000,000
Financial data for business segments
Electric Utilities' Revenues	41,000,000		35,000,000
Segment net income (loss)	0	[1],[2]	(16,000,000)	[1]
Total assets	1,093,000,000				1,077,000,000
Kemper Igcc [Member]
Financial data for business segments
Pre-tax charge to income	380,000,000		540,000,000		1,180,000,000
After tax charge to income	$ 234,700,000		$ 333,500,000		$ 728,700,000

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

[2] Segment net income (loss) for the traditional operating companies for the three months ended March 31, 2014 includes a $380.0 million pre-tax charge ($234.7 million after tax) for an estimated probable loss on the Kemper IGCC. See Note (B) under "Integrated Coal Gasification Combined Cycle – Kemper IGCC Schedule and Cost Estimate" herein for additional information.