Retirement Benefits - Actuarial Assumptions 1 (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plans [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.67%	4.17%
Annual salary increase, benefit obligation	4.46%	3.59%
Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	6.97%	7.15%	7.13%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.51%	4.04%
Annual salary increase, benefit obligation	4.46%	3.59%
Alabama Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.67%	4.18%
Annual salary increase, benefit obligation	4.46%	3.59%
Alabama Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	7.17%	7.34%	7.36%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.51%	4.04%
Annual salary increase, benefit obligation	4.46%	3.59%
Georgia Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.65%	4.18%
Annual salary increase, benefit obligation	4.46%	3.59%
Georgia Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	6.48%	6.75%	6.74%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.49%	4.03%
Annual salary increase, benefit obligation	4.46%	3.59%
Gulf Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.71%	4.18%
Annual salary increase, benefit obligation	4.46%	3.59%
Gulf Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	8.07%	8.08%	8.04%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.51%	4.04%
Annual salary increase, benefit obligation	4.46%	3.59%
Mississippi Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.69%	4.17%
Annual salary increase, benefit obligation	4.46%	3.59%
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Long-term return on plan assets on net periodic benefit costs	7.23%	7.30%	7.04%
Annual salary increase on net periodic benefit costs	3.59%	3.59%	3.59%
Discount rate, benefit obligation	4.47%	4.03%
Annual salary increase, benefit obligation	4.46%	3.59%
Interest Costs [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.17%	5.02%	4.26%
Interest Costs [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.04%	4.85%	4.05%
Interest Costs [Member] | Alabama Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.18%	5.02%	4.27%
Interest Costs [Member] | Alabama Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.04%	4.86%	4.06%
Interest Costs [Member] | Georgia Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.18%	5.02%	4.27%
Interest Costs [Member] | Georgia Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.03%	4.85%	4.04%
Interest Costs [Member] | Gulf Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.18%	5.02%	4.27%
Interest Costs [Member] | Gulf Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.04%	4.86%	4.06%
Interest Costs [Member] | Mississippi Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.17%	5.01%	4.26%
Interest Costs [Member] | Mississippi Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.03%	4.85%	4.04%
Service Costs [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.48%	5.02%	4.26%
Service Costs [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.39%	4.85%	4.05%
Service Costs [Member] | Alabama Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.49%	5.02%	4.27%
Service Costs [Member] | Alabama Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.40%	4.86%	4.06%
Service Costs [Member] | Georgia Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.49%	5.02%	4.27%
Service Costs [Member] | Georgia Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.39%	4.85%	4.04%
Service Costs [Member] | Gulf Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.48%	5.02%	4.27%
Service Costs [Member] | Gulf Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.38%	4.86%	4.06%
Service Costs [Member] | Mississippi Power [Member] | Pension Plans [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.49%	5.01%	4.26%
Service Costs [Member] | Mississippi Power [Member] | Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Discount rate on net periodic benefit costs	4.38%	4.85%	4.04%