Regulatory Matters - Schedule of SO Regulatory Assets and Liabilities (Details) - USD ($)
$ in Millions |
12 Months Ended |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 720
|
$ (1,894)
|
|
| Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Life of new issue |
50 years
|
|
|
| Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (1,872)
|
(1,879)
|
|
| Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (769)
|
(1,088)
|
|
| Alabama Power | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Life of new issue |
50 years
|
|
|
| Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (35)
|
(42)
|
|
| Regulatory amortization period |
5 years
|
|
|
| Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 2,378
|
232
|
|
| Customer refund liability, current |
55
|
|
|
| Customer refund |
$ 40
|
|
|
| Georgia Power | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Life of new issue |
34 years
|
|
|
| Deferred income tax credits |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (6,455)
|
(7,261)
|
|
| Deferred income tax credits | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(940)
|
(1,063)
|
|
| Deferred income tax credits | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(2,027)
|
(2,082)
|
|
| Deferred income tax credits | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(3,080)
|
(3,248)
|
|
| Other cost of removal obligations |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(2,297)
|
(2,684)
|
|
| Other cost of removal obligations | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(1,585)
|
(1,646)
|
|
| Other cost of removal obligations | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(497)
|
(609)
|
|
| Other cost of removal obligations | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(185)
|
(178)
|
|
| Customer refunds |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(293)
|
(188)
|
|
| Customer refunds | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(165)
|
(188)
|
|
| Property damage reserves-liability |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(76)
|
(135)
|
|
| Property damage reserves-liability | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(56)
|
(57)
|
|
| Over recovered regulatory clause revenues |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(47)
|
(155)
|
|
| Over recovered regulatory clause revenues | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(43)
|
(144)
|
|
| Other regulatory liabilities |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (132)
|
(104)
|
|
| Other regulatory liabilities | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory liability amortization period |
20 years
|
|
|
| Other regulatory liabilities | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (46)
|
(21)
|
|
| Other regulatory liabilities | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
(45)
|
(7)
|
|
| Other regulatory liabilities | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (9)
|
0
|
|
| Regulatory amortization period |
1 year
|
|
|
| Other regulatory liabilities | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ (7)
|
(3)
|
|
| Retiree benefit plans |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
3,658
|
3,931
|
|
| Regulatory asset |
$ 28
|
|
|
| Retiree benefit plans | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
15 years
|
|
|
| Retiree benefit plans | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 161
|
270
|
|
| Retiree benefit plans | Southern Company Gas | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
15 years
|
|
|
| Retiree benefit plans | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 947
|
946
|
|
| Retiree benefit plans | Alabama Power | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
15 years
|
|
|
| Retiree benefit plans | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
15 years
|
|
|
| Retiree benefit plans | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 1,295
|
1,313
|
|
| Retiree benefit plans | Georgia Power | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
14 years
|
|
|
| Asset retirement obligations-asset |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 2,933
|
1,133
|
|
| Asset retirement obligations-asset | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 143
|
95
|
|
| Regulatory amortization period |
48 years
|
|
|
| Asset retirement obligations-asset | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 2,644
|
945
|
|
| Deferred income tax charges |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 799
|
814
|
|
| Deferred income tax charges | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
80 years
|
|
|
| Deferred income tax charges | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 241
|
240
|
|
| Regulatory amortization period |
50 years
|
|
|
| Deferred income tax charges | Alabama Power | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
50 years
|
|
|
| Deferred income tax charges | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 34
|
36
|
|
| Deferred income tax charges | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
522
|
521
|
|
| Property damage reserves-asset |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
416
|
333
|
|
| Under recovered regulatory clause revenues |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
407
|
317
|
|
| Under recovered regulatory clause revenues | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 90
|
98
|
|
| Regulatory amortization period |
7 years
|
|
|
| Under recovered regulatory clause revenues | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 142
|
142
|
|
| Environmental remediation-asset |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
366
|
511
|
|
| Loss on reacquired debt |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
346
|
223
|
|
| Loss on reacquired debt | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
56
|
62
|
|
| Loss on reacquired debt | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
8
|
|
|
| Loss on reacquired debt | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
277
|
127
|
|
| Remaining net book value of retired assets |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 211
|
306
|
|
| Remaining net book value of retired assets | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
8 years
|
|
|
| Remaining net book value of retired assets | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
8 years
|
|
|
| Remaining net book value of retired assets | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 41
|
44
|
|
| Remaining net book value of retired assets | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 127
|
146
|
|
| Remaining net book value of retired assets | Georgia Power | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
3 years
|
|
|
| Vacation pay |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 182
|
183
|
|
| Regulatory amortization period |
1 year
|
|
|
| Vacation pay | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 71
|
70
|
|
| Regulatory amortization period |
1 year
|
|
|
| Vacation pay | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 9
|
|
|
| Vacation pay | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 91
|
91
|
|
| Regulatory amortization period |
1 year
|
|
|
| Long-term debt fair value adjustment |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 121
|
138
|
|
| Long-term debt fair value adjustment | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 121
|
138
|
|
| Long-term debt fair value adjustment | Southern Company Gas | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
20 years
|
|
|
| Deferred PPA charges |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 0
|
119
|
|
| Other regulatory assets |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 581
|
625
|
|
| Other regulatory assets | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
50 years
|
|
|
| Other regulatory assets | Southern Company Gas |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 59
|
79
|
|
| Other regulatory assets | Southern Company Gas | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
10 years
|
|
|
| Other regulatory assets | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 57
|
58
|
|
| Regulatory amortization period |
12 months
|
|
|
| Other regulatory assets | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 28
|
28
|
|
| Regulatory amortization period |
3 years
|
|
|
| Other regulatory assets | Mississippi Power | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
50 years
|
|
|
| Other regulatory assets | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 135
|
106
|
|
| Regulatory amortization period |
24 months
|
|
|
| Asset Group 1 | Maximum |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Regulatory amortization period |
10 years
|
|
|
| Kemper IGCC | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
$ 69
|
88
|
|
| Regulatory asset |
91
|
|
|
| Storm damage reserves | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Total regulatory assets (liabilities), net |
416
|
333
|
|
| Major storms |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Storm damage reserves |
74
|
41
|
$ 40
|
| Major storms | Alabama Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Storm damage reserves |
16
|
4
|
3
|
| Major storms | Mississippi Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Storm damage reserves |
1
|
3
|
4
|
| Major storms | Georgia Power |
|
|
|
| Schedule of Regulatory Assets and Liabilities [Line Items] |
|
|
|
| Storm damage reserves |
$ 30
|
$ 30
|
$ 30
|