Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Liabilities:
Weather derivative premium	$ 8	$ 11
Collateral already posted, aggregate fair value	277	193
Recurring
Assets:
Foreign currency derivatives	75
Non-qualified deferred compensation trusts:
Cash equivalents	766	1,455
Other investments	12	10
Total	3,387	3,995
Liabilities:
Contingent consideration	21	22
Total	1,057	816
Recurring | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	708	772
Recurring | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	226	286
Recurring | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	261	251
Recurring | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	83	68
Recurring | Pooled funds – fixed income
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	14
Recurring | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	314	336
Recurring | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	68	57
Recurring | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	45	29
Recurring | Cash and cash equivalents
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	16
Recurring | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	38	31
Recurring | Energy-related derivatives
Assets:
Energy-related derivatives	761	570
Liabilities:
Energy-related derivatives	964	733
Recurring | Interest rate derivatives
Assets:
Interest rate derivatives		1
Liabilities:
Interest rate derivatives	49	38
Recurring | Foreign currency derivatives
Assets:
Foreign currency derivatives	129
Liabilities:
Foreign currency derivatives	23	23
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Foreign currency derivatives	0
Non-qualified deferred compensation trusts:
Cash equivalents	765	1,455
Other investments	0	9
Total	1,962	2,587
Liabilities:
Contingent consideration	0	0
Total	648	480
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	601	690
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	53	62
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled funds – fixed income
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	24	21
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	16
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	34	19
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives
Assets:
Energy-related derivatives	469	331
Liabilities:
Energy-related derivatives	648	480
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate derivatives
Assets:
Interest rate derivatives		0
Liabilities:
Interest rate derivatives	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency derivatives
Assets:
Foreign currency derivatives	0
Liabilities:
Foreign currency derivatives	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Foreign currency derivatives	75
Non-qualified deferred compensation trusts:
Cash equivalents	1	0
Other investments	12	0
Total	1,380	1,378
Liabilities:
Contingent consideration	0	0
Total	388	314
Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	107	82
Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	173	224
Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	261	251
Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	83	68
Recurring | Significant Other Observable Inputs (Level 2) | Pooled funds – fixed income
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	14
Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	290	315
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	68	57
Recurring | Significant Other Observable Inputs (Level 2) | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0
Recurring | Significant Other Observable Inputs (Level 2) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	4	12
Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives
Assets:
Energy-related derivatives	292	239
Liabilities:
Energy-related derivatives	316	253
Recurring | Significant Other Observable Inputs (Level 2) | Interest rate derivatives
Assets:
Interest rate derivatives		1
Liabilities:
Interest rate derivatives	49	38
Recurring | Significant Other Observable Inputs (Level 2) | Foreign currency derivatives
Assets:
Foreign currency derivatives	129
Liabilities:
Foreign currency derivatives	23	23
Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Foreign currency derivatives	0
Non-qualified deferred compensation trusts:
Cash equivalents	0	0
Other investments	0	1
Total	0	1
Liabilities:
Contingent consideration	21	22
Total	21	22
Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Pooled funds – fixed income
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0
Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0
Recurring | Significant Unobservable Inputs (Level 3) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Interest rate derivatives
Assets:
Interest rate derivatives		0
Liabilities:
Interest rate derivatives	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Foreign currency derivatives
Assets:
Foreign currency derivatives	0
Liabilities:
Foreign currency derivatives	0	0
Recurring | Fair Value Measured at Net Asset Value Per Share
Non-qualified deferred compensation trusts:
Total	45	29
Recurring | Fair Value Measured at Net Asset Value Per Share | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	45	29
Alabama Power
Assets:
Energy-related derivatives	6	4
Liabilities:
Energy-related derivatives	10	10
Alabama Power | Recurring
Non-qualified deferred compensation trusts:
Cash equivalents	117	349
Other investments	12
Total	981	1,255
Alabama Power | Recurring | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	491	523
Alabama Power | Recurring | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	103	121
Alabama Power | Recurring | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	18	24
Alabama Power | Recurring | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	1
Alabama Power | Recurring | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	159	181
Alabama Power | Recurring | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	23	18
Alabama Power | Recurring | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	45	29
Alabama Power | Recurring | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	6	6
Alabama Power | Recurring | Energy-related derivatives
Assets:
Energy-related derivatives	6	4
Liabilities:
Energy-related derivatives	10	10
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Non-qualified deferred compensation trusts:
Cash equivalents	116	349
Other investments	0
Total	595	880
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	396	442
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	53	62
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	24	21
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	6	6
Alabama Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2)
Non-qualified deferred compensation trusts:
Cash equivalents	1	0
Other investments	12
Total	341	346
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	95	81
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	50	59
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	18	24
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	1
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	135	160
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	23	18
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives
Assets:
Energy-related derivatives	6	4
Liabilities:
Energy-related derivatives	10	10
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3)
Non-qualified deferred compensation trusts:
Cash equivalents	0	0
Other investments	0
Total	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Alabama Power | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Alabama Power | Recurring | Fair Value Measured at Net Asset Value Per Share
Non-qualified deferred compensation trusts:
Total	45	29
Alabama Power | Recurring | Fair Value Measured at Net Asset Value Per Share | Private equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	45	29
Georgia Power
Assets:
Energy-related derivatives	6	6
Liabilities:
Energy-related derivatives	23	24
Georgia Power | Recurring
Non-qualified deferred compensation trusts:
Cash equivalents		690
Total	879	1,625
Liabilities:
Total	23	24
Georgia Power | Recurring | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	206	249
Georgia Power | Recurring | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	119	166
Georgia Power | Recurring | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	243	227
Georgia Power | Recurring | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	82	68
Georgia Power | Recurring | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	155	155
Georgia Power | Recurring | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	45	40
Georgia Power | Recurring | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	23	24
Georgia Power | Recurring | Energy-related derivatives
Assets:
Energy-related derivatives	6	6
Liabilities:
Energy-related derivatives	21	19
Georgia Power | Recurring | Interest rate derivatives
Liabilities:
Interest rate derivatives	2	5
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Non-qualified deferred compensation trusts:
Cash equivalents		690
Total	224	950
Liabilities:
Total	0	0
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	205	248
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	19	12
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Georgia Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate derivatives
Liabilities:
Interest rate derivatives	0	0
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2)
Non-qualified deferred compensation trusts:
Cash equivalents		0
Total	655	675
Liabilities:
Total	23	24
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	1	1
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	119	166
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	243	227
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	82	68
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	155	155
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	45	40
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	4	12
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives
Assets:
Energy-related derivatives	6	6
Liabilities:
Energy-related derivatives	21	19
Georgia Power | Recurring | Significant Other Observable Inputs (Level 2) | Interest rate derivatives
Liabilities:
Interest rate derivatives	2	5
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3)
Non-qualified deferred compensation trusts:
Cash equivalents		0
Total	0	0
Liabilities:
Total	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Mortgage- and asset-backed securities
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Other
Nuclear decommissioning trusts:
Nuclear decommissioning trusts	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Georgia Power | Recurring | Significant Unobservable Inputs (Level 3) | Interest rate derivatives
Liabilities:
Interest rate derivatives	0	0
Mississippi Power
Assets:
Energy-related derivatives	3	3
Liabilities:
Energy-related derivatives	9	9
Mississippi Power | Recurring
Non-qualified deferred compensation trusts:
Cash equivalents	255	224
Total	258	227
Mississippi Power | Recurring | Energy-related derivatives
Assets:
Energy-related derivatives	3	2
Liabilities:
Energy-related derivatives	9	9
Mississippi Power | Recurring | Interest rate derivatives
Assets:
Interest rate derivatives		1
Mississippi Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Non-qualified deferred compensation trusts:
Cash equivalents	255	224
Total	255	224
Mississippi Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Mississippi Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate derivatives
Assets:
Interest rate derivatives		0
Mississippi Power | Recurring | Significant Other Observable Inputs (Level 2)
Non-qualified deferred compensation trusts:
Cash equivalents	0	0
Total	3	3
Mississippi Power | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives
Assets:
Energy-related derivatives	3	2
Liabilities:
Energy-related derivatives	9	9
Mississippi Power | Recurring | Significant Other Observable Inputs (Level 2) | Interest rate derivatives
Assets:
Interest rate derivatives		1
Mississippi Power | Recurring | Significant Unobservable Inputs (Level 3)
Non-qualified deferred compensation trusts:
Cash equivalents	0	0
Total	0	0
Mississippi Power | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Mississippi Power | Recurring | Significant Unobservable Inputs (Level 3) | Interest rate derivatives
Assets:
Interest rate derivatives		0
Southern Power
Assets:
Energy-related derivatives	79	132
Liabilities:
Energy-related derivatives	31	36
Southern Power | Recurring
Non-qualified deferred compensation trusts:
Cash equivalents	46	21
Total	125	153
Liabilities:
Contingent consideration	21	22
Total	52	58
Southern Power | Recurring | Energy-related derivatives
Assets:
Energy-related derivatives	4	3
Liabilities:
Energy-related derivatives	8	13
Southern Power | Recurring | Foreign currency derivatives
Assets:
Foreign currency derivatives	75	129
Liabilities:
Foreign currency derivatives	23	23
Southern Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Non-qualified deferred compensation trusts:
Cash equivalents	46	21
Total	46	21
Liabilities:
Contingent consideration	0	0
Total	0	0
Southern Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Southern Power | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency derivatives
Assets:
Foreign currency derivatives	0	0
Liabilities:
Foreign currency derivatives	0	0
Southern Power | Recurring | Significant Other Observable Inputs (Level 2)
Non-qualified deferred compensation trusts:
Cash equivalents	0	0
Total	79	132
Liabilities:
Contingent consideration	0	0
Total	31	36
Southern Power | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives
Assets:
Energy-related derivatives	4	3
Liabilities:
Energy-related derivatives	8	13
Southern Power | Recurring | Significant Other Observable Inputs (Level 2) | Foreign currency derivatives
Assets:
Foreign currency derivatives	75	129
Liabilities:
Foreign currency derivatives	23	23
Southern Power | Recurring | Significant Unobservable Inputs (Level 3)
Non-qualified deferred compensation trusts:
Cash equivalents	0	0
Total	0	0
Liabilities:
Contingent consideration	21	22
Total	21	22
Southern Power | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Assets:
Energy-related derivatives	0	0
Liabilities:
Energy-related derivatives	0	0
Southern Power | Recurring | Significant Unobservable Inputs (Level 3) | Foreign currency derivatives
Assets:
Foreign currency derivatives	0	0
Liabilities:
Foreign currency derivatives	0	0
Southern Company Gas
Assets:
Energy-related derivatives	741	554
Liabilities:
Energy-related derivatives	909	660
Weather derivative premium	8	11
Collateral already posted, aggregate fair value	277	193
Southern Company Gas | Energy-related derivatives
Liabilities:
Collateral already posted, aggregate fair value		6
Southern Company Gas | Recurring
Non-qualified deferred compensation trusts:
Cash equivalents	40
Total	814
Southern Company Gas | Recurring | Domestic equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	11
Southern Company Gas | Recurring | Foreign equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	4
Southern Company Gas | Recurring | Pooled funds – fixed income
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	14
Southern Company Gas | Recurring | Cash and cash equivalents
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	4
Southern Company Gas | Recurring | Energy-related derivatives
Assets:
Energy-related derivatives	741
Liabilities:
Energy-related derivatives	909
Southern Company Gas | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Non-qualified deferred compensation trusts:
Cash equivalents	40
Total	513
Southern Company Gas | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled funds – fixed income
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	4
Southern Company Gas | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives
Assets:
Energy-related derivatives	469
Liabilities:
Energy-related derivatives	648
Southern Company Gas | Recurring | Significant Other Observable Inputs (Level 2)
Non-qualified deferred compensation trusts:
Cash equivalents	0
Total	301
Southern Company Gas | Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	11
Southern Company Gas | Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	4
Southern Company Gas | Recurring | Significant Other Observable Inputs (Level 2) | Pooled funds – fixed income
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	14
Southern Company Gas | Recurring | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives
Assets:
Energy-related derivatives	272
Liabilities:
Energy-related derivatives	261
Southern Company Gas | Recurring | Significant Unobservable Inputs (Level 3)
Non-qualified deferred compensation trusts:
Cash equivalents	0
Total	0
Southern Company Gas | Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Significant Unobservable Inputs (Level 3) | Pooled funds – fixed income
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Non-qualified deferred compensation trusts:
Non-qualified deferred compensation trusts	0
Southern Company Gas | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Assets:
Energy-related derivatives	0
Liabilities:
Energy-related derivatives	$ 0
Predecessor | Southern Company Gas | Recurring | Energy-related derivatives
Assets:
Energy-related derivatives		554
Liabilities:
Energy-related derivatives		660
Predecessor | Southern Company Gas | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives
Assets:
Energy-related derivatives		331
Liabilities:
Energy-related derivatives		479
Predecessor | Southern Company Gas | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives
Assets:
Energy-related derivatives		223
Liabilities:
Energy-related derivatives		181
Predecessor | Southern Company Gas | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Assets:
Energy-related derivatives		0
Liabilities:
Energy-related derivatives		$ 0