Joint Ownership Agreements (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Plant Vogtle (nuclear) Units 1 and 2 [Member]
Jointly owned utility plant interests
Percent Ownership	45.70%
Amount of Investment	$ 3,296
Accumulated Depreciation	1,962
Plant Hatch (nuclear) [Member]
Jointly owned utility plant interests
Percent Ownership	50.10%
Amount of Investment	978
Accumulated Depreciation	545
Plant Miller (coal) Units 1 and 2 [Member]
Jointly owned utility plant interests
Percent Ownership	91.80%
Amount of Investment	1,389
Accumulated Depreciation	510
Joint Ownership Agreements (Textual) [Abstract]
Amount related to total construction work in progress	7
Plant Scherer (coal) Units 1 and 2 [Member]
Jointly owned utility plant interests
Percent Ownership	8.40%
Amount of Investment	157
Accumulated Depreciation	76
Joint Ownership Agreements (Textual) [Abstract]
Amount related to total construction work in progress	63
Plant Wansley (coal) [Member]
Jointly owned utility plant interests
Percent Ownership	53.50%
Amount of Investment	709
Accumulated Depreciation	225
Joint Ownership Agreements (Textual) [Abstract]
Amount related to total construction work in progress	36
Rocky Mountain (pumped storage) [Member]
Jointly owned utility plant interests
Percent Ownership	25.40%
Amount of Investment	175
Accumulated Depreciation	113
Intercession City (combustion turbine) [Member]
Jointly owned utility plant interests
Percent Ownership	33.30%
Amount of Investment	12
Accumulated Depreciation	4
Plant Stanton (combined cycle) Unit A [Member]
Jointly owned utility plant interests
Percent Ownership	65.00%
Amount of Investment	154
Accumulated Depreciation	$ 27