Income Taxes - Current and Deferred Income Tax Provisions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Federal -
Current	$ (177)	$ 175	$ 363
Deferred	1,266	695	386
Total federal taxes	1,089	870	749
State -
Current	(33)	93	(10)
Deferred	138	14	110
Total state taxes	105	107	100
Income taxes	1,194	977	849
Deferred tax assets	6,358	5,241
Alabama Power [Member]
Federal -
Current	110	198	243
Deferred	320	225	160
Total federal taxes	430	423	403
State -
Current	8	44	36
Deferred	68	45	39
Total state taxes	76	89	75
Income taxes	506	512	478
Deferred tax assets	1,511	1,141
Georgia Power [Member]
Federal -
Current	515	295	277
Deferred	176	366	374
Total federal taxes	691	661	651
State -
Current	81	82	(30)
Deferred	(3)	(14)	102
Total state taxes	78	68	72
Income taxes	769	729	723
Deferred tax assets	2,017	1,736
Gulf Power [Member]
Federal -
Current	(3)	23	5
Deferred	80	52	63
Total federal taxes	77	75	68
State -
Current	5	0	(2)
Deferred	10	13	14
Total state taxes	15	13	12
Income taxes	92	88	80
Deferred tax assets	216	171
Mississippi Power [Member]
Federal -
Current	(768)	(431)	23
Deferred	704	183	(343)
Total federal taxes	(64)	(248)	(320)
State -
Current	(81)	1	5
Deferred	73	(38)	(53)
Total state taxes	(8)	(37)	(48)
Income taxes	(72)	(285)	(368)
Deferred tax assets	1,400	1,251
Southern Power [Member]
Federal -
Current	12	179	(120)
Deferred	10	(166)	159
Total federal taxes	22	13	39
State -
Current	(32)	(14)	(5)
Deferred	31	(2)	12
Total state taxes	(1)	(16)	7
Income taxes	21	(3)	$ 46
Deferred tax assets	794	481
Unrealized Tax Credits [Member] | Southern Power [Member]
State -
Deferred tax assets	551	305
Unrealized Tax Credits [Member] | Deferred Charges Related To Income Taxes, Current [Member] | Other Noncurrent Assets [Member] | Southern Power [Member]
State -
Deferred tax assets	$ 246	$ 305