Components of the net periodic benefit costs for the three and nine months ended September 30, 2016 and 2015 were as follows:



Pension Plans	Southern Company			Alabama Power			Georgia Power			Gulf Power			Mississippi Power
	(in millions)
Three Months Ended September 30, 2016
Service cost	$	68		$	14		$	17		$	3		$	3
Interest cost	110			23			34			5			4
Expected return on plan assets	(203		)	(46		)	(64		)	(9		)	(9		)
Amortization:
Prior service costs	3			1			1			—			1
Net (gain)/loss	45			10			14			2			2
Net periodic pension cost	$	23		$	2		$	2		$	1		$	1
Nine Months Ended September 30, 2016
Service cost	$	192		$	43		$	52		$	9		$	9
Interest cost	311			71			102			14			14
Expected return on plan assets	(577		)	(138		)	(193		)	(26		)	(26		)
Amortization:
Prior service costs	10			2			4			1			1
Net (gain)/loss	120			30			41			5			5
Net periodic pension cost	$	56		$	8		$	6		$	3		$	3
Three Months Ended September 30, 2015
Service cost	$	65		$	14		$	18		$	3		$	3
Interest cost	111			26			38			5			5
Expected return on plan assets	(181		)	(44		)	(62		)	(8		)	(8		)
Amortization:
Prior service costs	6			2			2			1			—
Net (gain)/loss	53			14			19			2			3
Net periodic pension cost	$	54		$	12		$	15		$	3		$	3
Nine Months Ended September 30, 2015
Service cost	$	193		$	44		$	54		$	9		$	9
Interest cost	333			79			115			15			16
Expected return on plan assets	(543		)	(133		)	(188		)	(24		)	(25		)
Amortization:
Prior service costs	19			5			7			1			1
Net (gain)/loss	161			41			57			7			8
Net periodic pension cost	$	163		$	36		$	45		$	8		$	9



Postretirement Benefits	Southern Company			Alabama Power			Georgia Power			Gulf Power			Mississippi Power
	(in millions)
Three Months Ended September 30, 2016
Service cost	$	6		$	1		$	2		$	—		$	—
Interest cost	20			5			7			1			—
Expected return on plan assets	(16		)	(6		)	(6		)	—			—
Amortization:
Prior service costs	1			1			—			—			—
Net (gain)/loss	5			—			3			—			1
Net periodic postretirement benefit cost	$	16		$	1		$	6		$	1		$	1
Nine Months Ended September 30, 2016
Service cost	$	17		$	4		$	5		$	1		$	1
Interest cost	55			14			22			2			2
Expected return on plan assets	(44		)	(19		)	(17		)	(1		)	(1		)
Amortization:
Prior service costs	4			3			1			—			—
Net (gain)/loss	12			1			7			—			1
Net periodic postretirement benefit cost	$	44		$	3		$	18		$	2		$	3
Three Months Ended September 30, 2015
Service cost	$	6		$	1		$	2		$	1		$	—
Interest cost	20			5			9			—			1
Expected return on plan assets	(15		)	(6		)	(6		)	—			—
Amortization:
Prior service costs	1			2			—			—			—
Net (gain)/loss	4			—			2			—			—
Net periodic postretirement benefit cost	$	16		$	2		$	7		$	1		$	1
Nine Months Ended September 30, 2015
Service cost	$	17		$	4		$	5		$	1		$	1
Interest cost	59			15			26			2			3
Expected return on plan assets	(44		)	(19		)	(18		)	(1		)	(1		)
Amortization:
Prior service costs	3			3			—			—			—
Net (gain)/loss	13			1			8			—			—
Net periodic postretirement benefit cost	$	48		$	4		$	21		$	2		$	3