Contingencies and Regulatory Matters - Current And Actual Cost Estimate (Details) (Mississippi Power [Member], USD $)	12 Months Ended			0 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 22, 2013 Electricity Generation Plant, Non-Nuclear [Member]	Jan. 24, 2013 Electricity Generation Plant, Non-Nuclear [Member]	Dec. 31, 2013 Kemper IGCC [Member]		Dec. 31, 2013 Kemper IGCC [Member] Project Estimate [Member]		Dec. 31, 2013 Kemper IGCC [Member] Current Estimate [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap				$ 2,400,000,000	$ 2,400,000,000	$ 3,250,000,000	[1]	$ 2,400,000,000	[1],[2]	$ 4,060,000,000	[1]
Cost Of Lignite Mine And Equipment						230,000,000		210,000,000	[2]	230,000,000
Cost Of CO2 Pipeline Facilities						90,000,000		140,000,000	[2]	110,000,000
Cost Of AFUDC						280,000,000	[3]	170,000,000	[2],[3]	450,000,000	[3]
AFUDC Cost	8,500,000
Plant General Exceptions						70,000,000		50,000,000	[2]	100,000,000
Plant Regulatory Asset						70,000,000	[4]	0	[2],[4]	90,000,000	[4]
Total Kemper IGCC	2,880,000,000					3,990,000,000	[1]	2,970,000,000	[1],[2]	5,040,000,000	[1]
Loss Contingency, Estimate of Possible Loss	1,180,000,000
Noncash transactions - accrued property additions at year-end	$ 164,863,000	$ 214,863,000	$ 135,902,000

[1] The 2012 MPSC CPCN Order approved a construction cost cap of up to $2.88 billion, net of the DOE Grants and excluding the Cost Cap Exceptions.

[2] The 2010 Project Estimate is the certificated cost estimate adjusted to include the certificated estimate for the CO2 pipeline facilities which was approved in 2011 by the Mississippi PSC.

[3] Mississippi Power’s original estimate included recovery of financing costs during construction which was not approved by the Mississippi PSC in June 2012 as described in "Rate Recovery of Kemper IGCC Costs."

[4] The 2012 MPSC CPCN Order approved deferral of non-capital Kemper IGCC-related costs during construction as described in "Rate Recovery of Kemper IGCC Costs – Regulatory Assets."