Commitments - Estimated Long-term obligations (Details) $ in Millions	Dec. 31, 2016 USD ($)
Minimum Lease Payments, Operating Leases [Abstract]
2017	$ 152
2018	134
2019	113
2020	100
2021	90
2022 and thereafter	1,195
Total	1,784
Alabama Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	14
2018	10
2019	10
2020	8
2021	8
2022 and thereafter	10
Total	60
Georgia Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	19
2018	13
2019	9
2020	9
2021	8
2022 and thereafter	15
Total	73
2017	225
2018	218
2019	220
2020	216
2021	219
2022 and thereafter	1,608
Total	2,706
Gulf Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	8
2018	6
2019	1
2020	0
2021	0
2022 and thereafter	1
Total	16
Southern Company Gas [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	18
2018	17
2019	16
2020	15
2021	15
2022 and thereafter	38
Total	119
Barges and Rail Cars [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	31
2018	19
2019	10
2020	10
2021	8
2022 and thereafter	11
Total	89
Barges and Rail Cars [Member] | Georgia Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	12
2018	6
2019	3
2020	3
2021	2
2022 and thereafter	2
Total	28
Barges and Rail Cars [Member] | Gulf Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	7
2018	5
2019	0
2020	0
2021	0
2022 and thereafter	0
Total	12
Other Lease Payments [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	121
2018	115
2019	103
2020	90
2021	82
2022 and thereafter	1,184
Total	1,695
Other Lease Payments [Member] | Georgia Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	7
2018	7
2019	6
2020	6
2021	6
2022 and thereafter	13
Total	45
Other Lease Payments [Member] | Gulf Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	1
2018	1
2019	1
2020	0
2021	0
2022 and thereafter	1
Total	4
Railcars [Member] | Alabama Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	10
2018	7
2019	7
2020	6
2021	6
2022 and thereafter	9
Total	45
Vehicles And Other [Member] | Alabama Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	4
2018	3
2019	3
2020	2
2021	2
2022 and thereafter	1
Total	15
Purchased Power [Member]
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2017	242
2018	246
2019	249
2020	246
2021	249
2022 and thereafter	1,041
Total	2,273
Purchased Power [Member] | Alabama Power [Member]
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2017	40
2018	41
2019	43
2020	44
2021	46
2022 and thereafter	47
Total	261
Purchased Power [Member] | Gulf Power [Member]
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2017	79
2018	79
2019	79
2020	79
2021	79
2022 and thereafter	112
Total	507
Other Lease Payments [Member]
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2017	8
2018	7
2019	6
2020	5
2021	5
2022 and thereafter	43
Total	74
Affiliate Capital Lease PPA [Member] | Georgia Power [Member]
Minimum Lease Payments, Capital Leases [Abstract]
2017	22
2018	22
2019	23
2020	23
2021	24
2022 and thereafter	204
Total	318
Less: amounts representing executory costs	48
Net minimum lease payments	270
Less: amounts representing interest	128
Present value of net minimum lease payments	142
Affiliate Operating Lease PPA [Member] | Georgia Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	72
2018	63
2019	64
2020	65
2021	66
2022 and thereafter	479
Total	809
Non-Affiliate Operating Lease PPA [Member] | Georgia Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	123
2018	126
2019	127
2020	123
2021	124
2022 and thereafter	882
Total	1,505
Biomass PPAs Amount	197
Plant Vogtle Nuclear Units One and Two [Member] | Georgia Power [Member]
Minimum Lease Payments, Operating Leases [Abstract]
2017	8
2018	7
2019	6
2020	5
2021	5
2022 and thereafter	43
Total	$ 74