Contingencies and Regulatory Matters - Table - Current And Actual Cost Estimate (Details) - Mississippi Power [Member] - USD ($) $ in Millions				1 Months Ended	12 Months Ended			84 Months Ended
	Nov. 17, 2016	Apr. 08, 2016	Apr. 01, 2015	Jan. 31, 2013	Dec. 31, 2016	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2016
Loss Contingencies [Line Items]
AFUDC Cost			$ 14
Grants received from Department of Energy								$ (382)
Total Kemper IGCC							$ 2,880
Electricity Generation Plant, Non-Nuclear [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap				$ 2,400		$ 2,400
Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					$ 3,310
Plant Subject to Cost Cap	$ 68				5,440
Cost Of Lignite Mine And Equipment					230
Cost Of CO2 Pipeline Facilities					110
Cost Of AFUDC					750
Combined Cycle And Related Assets Placed In Service, Incremental					40
AFUDC Cost			$ 11
Plant General Exceptions					90
Plant Regulatory Asset					210
Grants received from Department of Energy		$ (137)			(140)			$ (245)
Total Kemper IGCC					$ 6,730
Purchase of Interest					100.00%			100.00%
Costs Subject to Cost Cap					$ 1,990
Kemper IGCC [Member] | Project Estimate [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap					2,400
Cost Of Lignite Mine And Equipment					210
Cost Of CO2 Pipeline Facilities					140
Cost Of AFUDC					170
Combined Cycle And Related Assets Placed In Service, Incremental					0
Plant General Exceptions					50
Plant Regulatory Asset					0
Grants received from Department of Energy					0
Total Kemper IGCC					2,970
Kemper IGCC [Member] | Current Estimate [Member]
Loss Contingencies [Line Items]
Plant Subject to Cost Cap					5,640
Cost Of Lignite Mine And Equipment					230
Cost Of CO2 Pipeline Facilities					110
Cost Of AFUDC					790
Combined Cycle And Related Assets Placed In Service, Incremental					40
Plant General Exceptions					100
Plant Regulatory Asset					220
Grants received from Department of Energy					(140)
Total Kemper IGCC					6,990
Costs for Combined Cycle and Related Assets In Service Expensed [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Total Kemper IGCC					830
Current Estimate [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Total Kemper IGCC					250
Gasifiers and Gas Clean-up Facilities [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					1,880
Lignite Mine Facility [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					310
CO2 Pipeline Facilities [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					110
Combined Cycle and Common Facilities [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					160
AFUDC [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					690
General Exceptions [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					70
Plant Inventory [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					30
Lignite Inventory [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					80
Regulatory and Other Deferred Assets [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					120
All Costs [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Recoverable Cost Above Maximum Cap Construction Cost					3,450
Costs Previously Expensed and Related Assets In Service [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Total Kemper IGCC					$ 80