Income Taxes (Tables)

9 Months Ended

Sep. 30, 2017

Income Tax Disclosure [Abstract]

Summary of Valuation Allowance

At September 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		64
Balance at September 30, 2017	$	46	$	19	$	82

Change in Unrecognized Tax Benefits

Changes during the nine months ended September 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	2			—			9
Tax positions from prior periods	(175		)	(17		)	(186		)
Reductions due to settlements	(290		)	—			(290		)
Balance as of September 30, 2017	$	2		$	—		$	17

Impact on Effective Tax Rate, If Recognized

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

	As of September 30, 2017				As of December 31, 2016
	Mississippi Power		Southern Company		Southern Company
	(in millions)
Tax positions impacting the effective tax rate	$	2	$	17	$	20
Tax positions not impacting the effective tax rate	—		—		464
Balance of unrecognized tax benefits	$	2	$	17	$	484