Income Taxes (Tables)

6 Months Ended

Jun. 30, 2017

Income Tax Disclosure [Abstract]

Summary of Valuation Allowance

At June 30, 2017, valuation allowances were as follows:

	Mississippi Power		Southern Company Gas		Southern Company
	(in millions)
Federal	$	—	$	18	$	18
State (net of federal benefit)	46		1		63
Balance at June 30, 2017	$	46	$	19	$	81

Change in Unrecognized Tax Benefits

Changes during the six months ended June 30, 2017 for unrecognized tax benefits were as follows:

	Mississippi Power		Southern Power		Southern Company
	(in millions)
Unrecognized tax benefits as of December 31, 2016	$	465	$	17	$	484
Tax positions from current periods	3		1		10
Tax positions from prior periods	—		1		7
Balance as of June 30, 2017	$	468	$	19	$	501

Impact on Effective Tax Rate, If Recognized

The impact on the effective tax rate, if recognized, is as follows:

	As of June 30, 2017						As of December 31, 2016
	Mississippi Power		Southern Power		Southern Company		Southern Company
	(in millions)
Tax positions impacting the effective tax rate	$	4	$	19	$	37	$	20
Tax positions not impacting the effective tax rate	464		—		464		464
Balance of unrecognized tax benefits	$	468	$	19	$	501	$	484