Contingencies and Regulatory Matters - Current And Actual Cost Estimate (Details) (Mississippi Power [Member], USD $)	1 Months Ended	12 Months Ended
	Jan. 31, 2013	Dec. 31, 2014
Loss Contingencies [Line Items]
AFUDC Cost		$ 19,200,000
Total Kemper IGCC	2,880,000,000
Loss Contingency, Estimate of Possible Loss		2,050,000,000
Electricity Generation Plant, Non-Nuclear [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap	2,400,000,000
Kemper IGCC [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap		4,230,000,000	[1]
Cost Of Lignite Mine And Equipment		230,000,000
Cost Of CO2 Pipeline Facilities		100,000,000
Cost Of AFUDC		450,000,000	[2],[3]
Combined Cycle And Related Assets Placed In Service, Incremental		0	[4]
Plant General Exceptions		70,000,000
Plant Regulatory Asset		120,000,000	[5],[6]
Total Kemper IGCC		5,200,000,000	[5],[7]
Kemper IGCC [Member] | Project Estimate [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap		2,400,000,000	[7],[8]
Cost Of Lignite Mine And Equipment		210,000,000	[8]
Cost Of CO2 Pipeline Facilities		140,000,000	[8]
Cost Of AFUDC		170,000,000	[5],[8],[9]
Combined Cycle And Related Assets Placed In Service, Incremental		0	[4],[8]
Plant General Exceptions		50,000,000	[8]
Plant Regulatory Asset		0	[5],[6],[8]
Total Kemper IGCC		2,970,000,000	[5],[7],[8]
Kemper IGCC [Member] | Current Estimate [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap		4,930,000,000	[1]
Cost Of Lignite Mine And Equipment		230,000,000
Cost Of CO2 Pipeline Facilities		110,000,000
Cost Of AFUDC		630,000,000	[2],[3]
Combined Cycle And Related Assets Placed In Service, Incremental		20,000,000	[4]
Plant General Exceptions		100,000,000
Plant Regulatory Asset		180,000,000	[5],[6]
Total Kemper IGCC		$ 6,200,000,000	[1],[5],[7]

[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. The Current Estimate and Actual Costs include non-incremental operating and maintenance costs related to the combined cycle and associated common facilities placed in service on August 9, 2014 that are subject to the $2.88 billion cost cap and excludes post-in-service costs for the lignite mine. See "Rate Recovery of Kemper IGCC Costs – 2013 MPSC Rate Order" for additional information.

[2] Amounts in the Current Estimate reflect estimated costs through March 31, 2016.

[3] The Company's original estimate included recovery of financing costs during construction rather than the accrual of AFUDC. This approach was not approved by the Mississippi PSC in 2012 as described in "Rate Recovery of Kemper IGCC Costs."

[4] Recovered through the ad valorem tax adjustment clause over a 12-month period beginning in April of the following year. See Note 3 under "Ad Valorem Tax Adjustment" for additional information.

[5] Asset retirement and removal assets and liabilities and deferred income tax assets are recovered, and removal assets and deferred income tax liabilities are amortized over the related property lives, which may range up to 49 years. Asset retirement and removal assets and liabilities will be settled and trued up following completion of the related activities.

[6] Recorded as earned by employees and recovered as paid, generally within one year. This includes both vacation and banked holiday pay.

[7] Recovered and amortized over the average remaining service period which may range up to 14 years. See Note 2 for additional information.

[8] Fuel-hedging assets and liabilities are recorded over the life of the underlying hedged purchase contracts, which generally do not exceed four years. Upon final settlement, costs are recovered through the ECM.

[9] Recorded and recovered (amortized) as approved by the Mississippi PSC.