Retirement Benefits - Fair Values of Pension Plan and Other Postretirement Benefit Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	$ 9,083	$ 9,647
Liabilities Fair Value
Fair Value, Plan Liabilities	(1)	(2)
Fair Value, Plan Assets and Liabilities	9,082	9,645
Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,313	2,408
Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,180	2,056
Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	454	699
Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	199	188
Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,140	1,135
Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	500	514
Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	145	663
Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1,517	1,414
Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	635	570
Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	834	905
Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	158	203
Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	104	103
Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	22	29
Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	7	6
Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	38	39
Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	42	41
Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	20	36
Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	370	381
Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	52	48
Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	21	19
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	3,121	3,070
Liabilities Fair Value
Fair Value, Plan Liabilities	(1)	(2)
Fair Value, Plan Assets and Liabilities	3,120	3,068
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,632	1,704
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,190	1,070
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	3
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	299	293
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	168	203
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	106	147
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	40	36
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	11	9
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	11	11
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	4,109	4,886
Liabilities Fair Value
Fair Value, Plan Liabilities	0	0
Fair Value, Plan Assets and Liabilities	4,109	4,886
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	681	704
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	990	986
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	454	699
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	199	188
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,140	1,135
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	500	514
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	145	660
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	604	646
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	52	56
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	64	67
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	22	29
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	7	6
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	38	39
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	42	41
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	9	27
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	370	381
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Liabilities Fair Value
Fair Value, Plan Liabilities	0	0
Fair Value, Plan Assets and Liabilities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,853	1,691
Liabilities Fair Value
Fair Value, Plan Liabilities	0	0
Fair Value, Plan Assets and Liabilities	1,853	1,691
Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1,218	1,121
Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	635	570
Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	62	56
Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	41	37
Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	21	19
Alabama Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	2,241	2,385
Alabama Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	571	595
Alabama Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	538	508
Alabama Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	112	173
Alabama Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	49	47
Alabama Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	280	280
Alabama Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	123	127
Alabama Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	36	164
Alabama Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	375	350
Alabama Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	157	141
Alabama Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	361	391
Alabama Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	65	84
Alabama Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	26	25
Alabama Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	8	10
Alabama Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Alabama Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	13	14
Alabama Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	6	6
Alabama Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	3	8
Alabama Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	212	217
Alabama Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	19	18
Alabama Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	7	7
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	771	759
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	403	421
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	294	264
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	1
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	74	73
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	77	94
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	57	76
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	14	13
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	5	5
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,012	1,208
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	168	174
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	244	244
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	112	173
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	49	47
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	280	280
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	123	127
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	36	163
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	263	277
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	8	8
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	12	12
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	8	10
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	13	14
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	6	6
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	2	8
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	212	217
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Alabama Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	458	418
Alabama Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	301	277
Alabama Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	157	141
Alabama Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	21	20
Alabama Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	14	13
Alabama Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	7	7
Georgia Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	3,143	3,368
Liabilities Fair Value
Fair Value, Plan Liabilities		(1)
Fair Value, Plan Assets and Liabilities		3,367
Georgia Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	801	841
Georgia Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	755	717
Georgia Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	157	244
Georgia Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	69	66
Georgia Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	394	398
Georgia Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	173	179
Georgia Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	50	231
Georgia Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	524	493
Georgia Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	220	199
Georgia Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	364	401
Georgia Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	66	93
Georgia Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	53	56
Georgia Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	5	7
Georgia Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Georgia Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	12	12
Georgia Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	30	29
Georgia Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	16	19
Georgia Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	158	162
Georgia Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	15	15
Georgia Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	7	6
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,080	1,071
Liabilities Fair Value
Fair Value, Plan Liabilities		(1)
Fair Value, Plan Assets and Liabilities		1,070
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	565	595
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	412	373
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	1
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	103	102
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	55	75
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	30	53
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	12	11
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	10	8
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	3	3
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,422	1,707
Liabilities Fair Value
Fair Value, Plan Liabilities		0
Fair Value, Plan Assets and Liabilities		1,707
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	236	246
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	343	344
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	157	244
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	69	66
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	394	398
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	173	179
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	50	230
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	290	308
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	36	40
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	41	45
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	5	7
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	12	12
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	30	29
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	6	11
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	158	162
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Liabilities Fair Value
Fair Value, Plan Liabilities		0
Fair Value, Plan Assets and Liabilities		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Georgia Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	641	590
Liabilities Fair Value
Fair Value, Plan Liabilities		0
Fair Value, Plan Assets and Liabilities		590
Georgia Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	421	391
Georgia Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	220	199
Georgia Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	19	18
Georgia Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	12	12
Georgia Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	7	6
Gulf Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	412	433
Gulf Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	104	109
Gulf Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	99	92
Gulf Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	21	31
Gulf Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	9	8
Gulf Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	51	51
Gulf Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23	23
Gulf Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	7	30
Gulf Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	69	63
Gulf Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	29	26
Gulf Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	17	18
Gulf Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4	4
Gulf Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4	4
Gulf Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	1
Gulf Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Gulf Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	3	3
Gulf Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	141	138
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	73	77
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	54	48
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	14	13
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	7	6
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	3	3
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1	0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	187	219
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	31	32
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	45	44
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	21	31
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	9	8
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	51	51
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23	23
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	7	30
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	7	9
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	1
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	1
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Gulf Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	84	76
Gulf Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	55	50
Gulf Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	29	26
Gulf Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	3	3
Gulf Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Gulf Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Mississippi Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	423	443
Mississippi Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	108	110
Mississippi Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	101	94
Mississippi Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	21	32
Mississippi Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	9	9
Mississippi Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	53	53
Mississippi Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23	24
Mississippi Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	7	30
Mississippi Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	71	65
Mississippi Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	30	26
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	23	24
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4	5
Mississippi Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4	4
Mississippi Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	6	6
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1	2
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	4	3
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	145	141
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	76	78
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	55	49
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	14	14
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	7	7
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	3	3
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	191	225
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	32	32
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	46	45
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	21	32
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	9	9
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	53	53
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23	24
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	7	30
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	12	14
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1	2
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	6	6
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2	2
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1	1
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	1
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	0
Mississippi Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	87	77
Mississippi Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	57	51
Mississippi Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	30	26
Mississippi Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	4	3
Mississippi Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	3	2
Mississippi Power [Member] | Fair Value, Inputs, Net Asset Value As A Practical Expedient [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	$ 1	$ 1