v3.10.0.1
Stock Compensation (Tables)
 12 Months Ended
Dec. 31, 2018
Equity [Abstract]  
Schedule of Employees Participating in Stock-Based Compensation Programs
At December 31, 2018, the number of current and former employees participating in stock-based compensation programs for the registrants was as follows:
 
Southern Company
Alabama Power
Georgia Power
Mississippi Power
Southern Power
Southern Company Gas
Number of employees
4,716

745

822

164

95

285
Assumptions used in the pricing model and the weighted average grant-date fair value of performance share award units granted
The following table shows the assumptions used in the pricing model and the weighted average grant-date fair value of TSR awards granted:
Year Ended December 31
2018
 
2017
 
2016
Expected volatility
14.9%
 
15.6%
 
15.0%
Expected term (in years)
3
 
3
 
3
Interest rate
2.4%
 
1.4%
 
0.8%
Weighted average grant-date fair value
$43.75
 
$49.08
 
$45.06
Schedule of Compensation Costs and Related Tax Benefits
Total intrinsic value of options exercised, and the related tax benefit, for the years ended December 31, 2018, 2017, and 2016 are presented below:
Year Ended December 31
2018
 
2017
 
2016
 
(in millions)
Southern Company
 
 
 
 
 
Intrinsic value of options exercised
$
9

 
$
64

 
$
120

Tax benefit of options exercised
2

 
25

 
46

Alabama Power
 
 
 
 
 
Intrinsic value of options exercised
$
2

 
$
12

 
$
21

Tax benefit of options exercised
—

 
5

 
8

Georgia Power
 
 
 
 
 
Intrinsic value of options exercised
$
2

 
$
13

 
$
18

Tax benefit of options exercised
—

 
5

 
7

Mississippi Power
 
 
 
 
 
Intrinsic value of options exercised
$
1

 
$
2

 
$
4

Tax benefit of options exercised
—

 
1

 
2

Total PSU compensation cost, and the related tax benefit recognized in income, for the years ended December 31, 2018, 2017, and 2016 are as follows:
 
2018
 
2017
 
2016
 
(in millions)
Southern Company
 
 
 
 
 
Compensation cost recognized in income
$
91

 
$
74

 
$
96

Tax benefit of compensation cost recognized in income
24

 
29

 
37

Alabama Power
 
 
 
 
 
Compensation cost recognized in income
$
11

 
$
9

 
$
15

Tax benefit of compensation cost recognized in income
3

 
4

 
6

Georgia Power
 
 
 
 
 
Compensation cost recognized in income
$
11

 
$
10

 
$
15

Tax benefit of compensation cost recognized in income
3

 
4

 
6

Mississippi Power
 
 
 
 
 
Compensation cost recognized in income
$
3

 
$
2

 
$
4

Tax benefit of compensation cost recognized in income
1

 
1

 
1

Southern Power
 
 
 
 
 
Compensation cost recognized in income
$
4

 
N/A

 
N/A

Tax benefit of compensation cost recognized in income
1

 
N/A

 
N/A

Southern Company Gas
 
 
 
 
 
Compensation cost recognized in income
$
11

 
$
8

 
N/A

Tax benefit of compensation cost recognized in income
3

 
3

 
N/A
Share-based Compensation, Stock Options, Activity
Southern Company's activity in the stock option program for 2018 is summarized below:
 
Shares Subject to Option
 
Weighted Average Exercise Price
 
(in millions)
 
 
Outstanding at December 31, 2017
18.6

 
$
41.68

Exercised
1.1

 
37.82

Outstanding and Exercisable at December 31, 2018
17.5

 
$
41.92
Schedule of Aggregate and Total Intrinsic Value Of Options Exercised
At December 31, 2018, the aggregate intrinsic value for the options outstanding and exercisable was as follows:
 
Southern Company
Alabama Power
Georgia Power
Mississippi Power
 
(in millions)
Total intrinsic value for outstanding and exercisable options
$
39

$
5

$
13

$
1