Retirement Benefits - Actuarial Assumptions 1 (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Discount rate:
Annual salary increase	3.59%	3.59%	3.59%	3.84%
Pension Plans [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.17%	5.02%	4.26%	4.98%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Other Postretirement Benefits [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.04%	4.85%	4.05%	4.88%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	7.15%	7.13%	7.29%
Alabama Power [Member]
Discount rate:
Annual salary increase	3.59%	3.59%	3.59%	3.84%
Alabama Power [Member] | Pension Plans [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.18%	5.02%	4.27%	4.98%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Alabama Power [Member] | Other Postretirement Benefits [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.04%	4.86%	4.06%	4.88%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	7.34%	7.36%	7.19%
Georgia Power [Member]
Discount rate:
Annual salary increase	3.59%	3.59%	3.59%	3.84%
Georgia Power [Member] | Pension Plans [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.18%	5.02%	4.27%	4.98%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Georgia Power [Member] | Other Postretirement Benefits [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.03%	4.85%	4.04%	4.87%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	6.75%	6.74%	7.24%
Gulf Power [Member]
Discount rate:
Annual salary increase	3.59%	3.59%	3.59%	3.84%
Gulf Power [Member] | Pension Plans [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.18%	5.02%	4.27%	4.98%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Gulf Power [Member] | Other Postretirement Benefits [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.04%	4.86%	4.06%	4.88%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	8.08%	8.04%	8.02%
Mississippi Power [Member]
Discount rate:
Annual salary increase	3.59%	3.59%	3.59%	3.84%
Mississippi Power [Member] | Pension Plans [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.17%	5.01%	4.26%	4.98%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	8.20%	8.20%	8.20%
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Discount rate:
Discount rate on net periodic benefit costs	4.03%	4.85%	4.04%	4.87%
Long-term return on plan assets:
Long-term return on plan assets on net periodic benefit costs	7.30%	7.04%	6.96%