Income Taxes (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 208		$ 188
Effective tax rate	30.40%	32.90%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits as of December 31, 2015	$ 433
Tax positions from current periods	10
Balance as of June 30, 2016	443
Tax positions impacting the effective tax rate	20		10
Tax positions not impacting the effective tax rate	423		423
Kemper IGCC [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of June 30, 2016	423
Unrecognized tax benefit, associated interest	$ 15
Mississippi Power [Member]
Income Tax Contingency [Line Items]
Effective tax rate	(205.60%)	19.00%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits as of December 31, 2015	$ 421
Tax positions from current periods	0
Balance as of June 30, 2016	421
Tax positions impacting the effective tax rate	(2)
Tax positions not impacting the effective tax rate	423
Mississippi Power [Member] | Kemper IGCC [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of June 30, 2016	423
Unrecognized tax benefit, associated interest	$ 15
Southern Power [Member]
Income Tax Contingency [Line Items]
Effective tax rate	(74.00%)	13.70%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits as of December 31, 2015	$ 8
Tax positions from current periods	9
Balance as of June 30, 2016	17
Tax positions impacting the effective tax rate	17
Tax positions not impacting the effective tax rate	0
Investment Tax Credit Carryforward [Member]
Income Tax Contingency [Line Items]
Tax Credit Carryforward, Amount	801		554
Investment Tax Credit Carryforward [Member] | Southern Power [Member]
Income Tax Contingency [Line Items]
Tax Credit Carryforward, Amount	784		551
General Business Tax Credit Carryforward [Member]
Income Tax Contingency [Line Items]
Tax Credit Carryforward, Amount	16		1
General Business Tax Credit Carryforward [Member] | Southern Power [Member]
Income Tax Contingency [Line Items]
Tax Credit Carryforward, Amount	$ 16		$ 1