Joint Ownership Agreements (Details) $ in Millions	Dec. 31, 2016 USD ($) MW	Aug. 31, 2016
Alabama Power [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	1,000
Company Ownership	14.00%
Alabama Power [Member] | Plant Miller (coal) Units 1 and 2 [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	1,320
Company Ownership	91.84%
Plant in service	$ 1,657
Accumulated depreciation	587
Construction Work in Progress	$ 23
Alabama Power [Member] | Greene County [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	500
Company Ownership	60.00%
Plant in service	$ 168
Accumulated depreciation	66
Construction Work in Progress	$ 1
Alabama Power [Member] | SEGCO [Member]
Jointly owned utility plant interests
Company Ownership	86.00%
Georgia Power [Member] | Plant Vogtle Nuclear Units One and Two [Member]
Jointly owned utility plant interests
Company Ownership	45.70%
Plant in service	$ 3,545
Accumulated depreciation	2,111
Construction Work in Progress	$ 74
Georgia Power [Member] | Plant Hatch (nuclear) [Member]
Jointly owned utility plant interests
Company Ownership	50.10%
Plant in service	$ 1,297
Accumulated depreciation	585
Construction Work in Progress	$ 81
Georgia Power [Member] | Plant Scherer (coal) Units 1 and 2 [Member]
Jointly owned utility plant interests
Company Ownership	8.40%
Plant in service	$ 258
Accumulated depreciation	90
Construction Work in Progress	$ 3
Georgia Power [Member] | Plant Wansley (coal) [Member]
Jointly owned utility plant interests
Company Ownership	53.50%
Plant in service	$ 1,046
Accumulated depreciation	308
Construction Work in Progress	$ 12
Georgia Power [Member] | Rocky Mountain (pumped storage) [Member]
Jointly owned utility plant interests
Company Ownership	25.40%
Plant in service	$ 181
Accumulated depreciation	129
Construction Work in Progress	$ 0
Georgia Power [Member] | Plant Scherer Unit 3 (coal) [Member]
Jointly owned utility plant interests
Company Ownership	75.00%
Plant in service	$ 1,203
Accumulated depreciation	458
Construction Work in Progress	$ 23
Georgia Power [Member] | Intercession City (combustion turbine) [Member]
Jointly owned utility plant interests
Company Ownership		33.00%
Georgia Power [Member] | Vogtle Units 3 and 4 [Member]
Jointly owned utility plant interests
Company Ownership	45.70%
Gulf Power [Member] | Plant Scherer Unit 3 (coal) [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	818
Company Ownership	25.00%
Plant in service	$ 398
Accumulated depreciation	143
Construction Work in Progress	$ 7
Gulf Power [Member] | Plant Daniel Units 1 and 2 [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	1,000
Company Ownership	50.00%
Plant in service	$ 680
Accumulated depreciation	202
Construction Work in Progress	$ 7
Mississippi Power [Member] | Plant Daniel Units 1 and 2 [Member]
Jointly owned utility plant interests
Company Ownership	50.00%
Southern Power [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	659
Southern Power [Member] | Plant Stanton (combined cycle) Unit A [Member]
Jointly owned utility plant interests
Company Ownership	65.00%
Plant in service	$ 155
Accumulated depreciation	58
Construction Work in Progress	$ 0
Gulf Power [Member] | Mississippi Power [Member] | Plant Daniel Units 1 and 2 [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	1,000
Company Ownership	50.00%
Plant in service	$ 695
Accumulated depreciation	173
Construction Work in Progress	$ 15
Alabama Power [Member] | Mississippi Power [Member] | Greene County [Member]
Jointly owned utility plant interests
Total megawatt capacity | MW	500
Company Ownership	40.00%
Plant in service	$ 165
Accumulated depreciation	48
Construction Work in Progress	$ 0