Summary of Significant Accounting Policies - Accumulated Provisions and Estimated Costs For Decommissioning (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Alabama Power [Member]
Accumulated Provisions for Decommissioning
Total	$ 775	$ 734
Decommissioning
Total site study costs	1,442
Alabama Power [Member] | Plant Farley [Member]
Decommissioning
Beginning Year	2037
Completion Year	2076
Alabama Power [Member] | Accumulated Provisions for Decommissioning External Trust Funds [Member]
Accumulated Provisions for Decommissioning
Total	754	713
Alabama Power [Member] | Accumulated Provisions for Decommissioning Internal Reserves [Member]
Accumulated Provisions for Decommissioning
Total	21	21
Alabama Power [Member] | Site Study Cost Radiated Structures [Member]
Decommissioning
Total site study costs	1,362
Alabama Power [Member] | Site Study Cost Non-Radiated Structures [Member]
Decommissioning
Total site study costs	80
Plant Farley [Member]
Accumulated Provisions for Decommissioning
Total	775	734
Decommissioning
Beginning Year	2037
Completion Year	2076
Total site study costs	1,442
Plant Farley [Member] | Accumulated Provisions for Decommissioning External Trust Funds [Member]
Accumulated Provisions for Decommissioning
Total	754	713
Plant Farley [Member] | Accumulated Provisions for Decommissioning Internal Reserves [Member]
Accumulated Provisions for Decommissioning
Total	21	21
Plant Farley [Member] | Site Study Cost Radiated Structures [Member]
Decommissioning
Total site study costs	1,362
Plant Farley [Member] | Spent Fuel Management [Member]
Decommissioning
Total site study costs	0
Plant Farley [Member] | Site Study Cost Non-Radiated Structures [Member]
Decommissioning
Total site study costs	80
Plant Hatch [Member]
Accumulated Provisions for Decommissioning
Total	496	469
Decommissioning
Beginning Year	2034
Completion Year	2068
Total site study costs	731
Plant Hatch [Member] | Accumulated Provisions for Decommissioning External Trust Funds [Member]
Accumulated Provisions for Decommissioning
Total	496	469
Plant Hatch [Member] | Accumulated Provisions for Decommissioning Internal Reserves [Member]
Accumulated Provisions for Decommissioning
Total	0	0
Plant Hatch [Member] | Site Study Cost Radiated Structures [Member]
Decommissioning
Total site study costs	549
Plant Hatch [Member] | Spent Fuel Management [Member]
Decommissioning
Total site study costs	131
Plant Hatch [Member] | Site Study Cost Non-Radiated Structures [Member]
Decommissioning
Total site study costs	51
Plant Hatch [Member] | Georgia Power [Member]
Decommissioning
Beginning Year	2034
Completion Year	2068
Total site study costs	731
External trust funds	496
Plant Hatch [Member] | Georgia Power [Member] | Site Study Cost Radiated Structures [Member]
Decommissioning
Total site study costs	549
Plant Hatch [Member] | Georgia Power [Member] | Spent Fuel Management [Member]
Decommissioning
Total site study costs	131
Plant Hatch [Member] | Georgia Power [Member] | Site Study Cost Non-Radiated Structures [Member]
Decommissioning
Total site study costs	51
Plant Vogtle [Member]
Accumulated Provisions for Decommissioning
Total	293	277
Decommissioning
Beginning Year	2047
Completion Year	2072
Total site study costs	644
Plant Vogtle [Member] | Accumulated Provisions for Decommissioning External Trust Funds [Member]
Accumulated Provisions for Decommissioning
Total	293	277
Plant Vogtle [Member] | Accumulated Provisions for Decommissioning Internal Reserves [Member]
Accumulated Provisions for Decommissioning
Total	0	0
Plant Vogtle [Member] | Site Study Cost Radiated Structures [Member]
Decommissioning
Total site study costs	453
Plant Vogtle [Member] | Spent Fuel Management [Member]
Decommissioning
Total site study costs	115
Plant Vogtle [Member] | Site Study Cost Non-Radiated Structures [Member]
Decommissioning
Total site study costs	76
Plant Vogtle [Member] | Georgia Power [Member]
Decommissioning
Beginning Year	2047
Completion Year	2072
Total site study costs	644
External trust funds	293
Plant Vogtle [Member] | Georgia Power [Member] | Site Study Cost Radiated Structures [Member]
Decommissioning
Total site study costs	453
Plant Vogtle [Member] | Georgia Power [Member] | Spent Fuel Management [Member]
Decommissioning
Total site study costs	115
Plant Vogtle [Member] | Georgia Power [Member] | Site Study Cost Non-Radiated Structures [Member]
Decommissioning
Total site study costs	$ 76