Regulatory Matters - Schedule of APC Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 720	$ (1,894)
Fuel hedging asset and liabilities amortization period	3 years
Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Life of new issue	50 years
Deferred income tax credits
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ (6,455)	(7,261)
Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	(2,297)	(2,684)
Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	(132)	(104)
Retiree benefit plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 3,658	3,931
Retiree benefit plans | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	15 years
Deferred income tax charges
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 799	814
Deferred income tax charges | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	80 years
Regulatory clauses
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 407	317
Vacation pay
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 182	183
Regulatory amortization period	1 year
Loss on reacquired debt
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 346	223
Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 581	625
Other regulatory assets | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	50 years
Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 211	306
Remaining net book value of retired assets | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	8 years
Alabama Power
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ (769)	(1,088)
Medicare drug subsidy obligation related to subsidiary	$ 10	13
Alabama Power | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Life of new issue	50 years
Alabama Power | Asset retirement obligations-asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 147	(33)
Alabama Power | Deferred income tax credits
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	(2,027)	(2,082)
Alabama Power | Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	(497)	(609)
Alabama Power | Rate RSE refund
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	(109)	0
Alabama Power | Natural disaster reserve
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	(20)	(38)
Alabama Power | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	(45)	(7)
Alabama Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	33
Alabama Power | Retiree benefit plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 947	946
Alabama Power | Retiree benefit plans | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	15 years
Alabama Power | Deferred income tax charges
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 241	240
Regulatory amortization period	50 years
Alabama Power | Deferred income tax charges | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	50 years
Alabama Power | Under recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 176	53
Alabama Power | Regulatory clauses
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	142	142
Alabama Power | Vacation pay
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 71	70
Regulatory amortization period	1 year
Alabama Power | Loss on reacquired debt
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 56	62
Alabama Power | Nuclear outage
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 49	56
Regulatory amortization period	18 months
Alabama Power | Nuclear outage | Maximum
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	10 years
Alabama Power | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 43	54
Alabama Power | Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total regulatory assets (liabilities), net	$ 57	$ 58
Regulatory amortization period	12 months
Alabama Power | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory amortization period	8 years