Leases - Balance Sheet Amounts Recorded for Operating and Financing Leases (Details) $ in Millions	Jun. 30, 2019 USD ($)
Operating Leases
Operating lease ROU assets, net, including held for sale	$ 1,907
Operating lease ROU assets, net	1,862
Operating lease obligations - current, including held for sale	241
Operating lease obligations - current	228
Operating lease obligations - non current, including held for sale	1,733
Operating lease obligations - non current	1,702
Total operating lease obligations, including held for sale	1,974
Finance Leases
Finance lease ROU assets, net	237
Finance lease obligations - current	24
Finance lease obligations - noncurrent	220
Total finance lease obligations	244
ALABAMA POWER CO
Operating Leases
Operating lease ROU assets, net	152
Operating lease obligations - current	48
Operating lease obligations - non current	137
Total operating lease obligations	185
Finance Leases
Finance lease ROU assets, net	5
Finance lease obligations - current	1
Finance lease obligations - noncurrent	4
Total finance lease obligations	5
GEORGIA POWER CO
Operating Leases
Operating lease ROU assets, net	1,492
Operating lease obligations - current	140
Operating lease obligations - non current	1,377
Total operating lease obligations	1,517
Finance Leases
Finance lease ROU assets, net	142
Finance lease obligations - current	10
Finance lease obligations - noncurrent	159
Total finance lease obligations	169
MISSISSIPPI POWER CO
Operating Leases
Operating lease ROU assets, net	7
Operating lease obligations - current	2
Operating lease obligations - non current	5
Total operating lease obligations	7
Finance Leases
Finance lease ROU assets, net	0
Finance lease obligations - current	0
Finance lease obligations - noncurrent	0
Total finance lease obligations	0
SOUTHERN POWER CO
Operating Leases
Operating lease ROU assets, net	370
Operating lease obligations - current	22
Operating lease obligations - non current	373
Total operating lease obligations	395
Finance Leases
Finance lease ROU assets, net	0
Finance lease obligations - current	0
Finance lease obligations - noncurrent	0
Total finance lease obligations	0
SOUTHERN Co GAS
Operating Leases
Operating lease ROU assets, net	95
Operating lease obligations - current	15
Operating lease obligations - non current	79
Total operating lease obligations	94
Finance Leases
Finance lease ROU assets, net	0
Finance lease obligations - current	0
Finance lease obligations - noncurrent	0
Total finance lease obligations	$ 0