Leases - Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lease cost
Operating lease cost	$ 77	$ 147
Finance lease cost:
Amortization of ROU assets	7	14
Interest on lease obligations	3	6
Total finance lease cost	10	20
Short-term lease costs	13	30
Variable lease cost	29	48
Sublease income	0	0
Total lease cost	129	245
ALABAMA POWER CO
Lease cost
Operating lease cost	13	20
Finance lease cost:
Amortization of ROU assets	0	0
Interest on lease obligations	0	0
Total finance lease cost	0	0
Short-term lease costs	6	11
Variable lease cost	1	1
Sublease income	0	0
Total lease cost	20	32
GEORGIA POWER CO
Lease cost
Operating lease cost	50	99
Finance lease cost:
Amortization of ROU assets	4	7
Interest on lease obligations	4	9
Total finance lease cost	8	16
Short-term lease costs	6	12
Variable lease cost	25	41
Sublease income	0	0
Total lease cost	89	168
MISSISSIPPI POWER CO
Lease cost
Operating lease cost	1	1
Finance lease cost:
Amortization of ROU assets	0	0
Interest on lease obligations	0	0
Total finance lease cost	0	0
Short-term lease costs	0	0
Variable lease cost	0	0
Sublease income	0	0
Total lease cost	1	1
SOUTHERN POWER CO
Lease cost
Operating lease cost	7	14
Finance lease cost:
Amortization of ROU assets	0	0
Interest on lease obligations	0	0
Total finance lease cost	0	0
Short-term lease costs	0	0
Variable lease cost	1	3
Sublease income	0	0
Total lease cost	8	17
SOUTHERN Co GAS
Lease cost
Operating lease cost	5	9
Finance lease cost:
Amortization of ROU assets	0	0
Interest on lease obligations	0	0
Total finance lease cost	0	0
Short-term lease costs	0	0
Variable lease cost	0	0
Sublease income	0	0
Total lease cost	$ 5	$ 9