Commitments (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) Railcar	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Recorded Unconditional Purchase Obligation [Line Items]
Fuel expense	$ 4,750,000,000	$ 6,005,000,000	$ 5,510,000,000
Expense Under Purchase Power Agreements Accounted For As Operating Leases	227,000,000	198,000,000	157,000,000
Operating Leases, Rent Expense	130,000,000	118,000,000	123,000,000
Leasing commitment, 2017	103,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	81,000,000
Leasing commitment, 2019	61,000,000
Leasing commitment, 2020	53,000,000
Leasing commitment, 2021 and thereafter	706,000,000
Operating leases, future minimum lease payments due	1,125,000,000
Senior Notes	19,100,000,000	18,200,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	121,000,000
Barges and Rail Cars [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Leasing commitment, 2017	25,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	14,000,000
Leasing commitment, 2019	6,000,000
Leasing commitment, 2020	6,000,000
Leasing commitment, 2021 and thereafter	16,000,000
Operating leases, future minimum lease payments due	107,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	40,000,000
Alabama Power and Georgia Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases, future minimum lease payments due	48,000,000
Alabama Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Fuel expense	1,342,000,000	1,605,000,000	1,631,000,000
Expense Under Purchase Power Agreements Accounted For As Operating Leases	$ 38,000,000	37,000,000	30,000,000
Jointly Owned Utility Plant, Proportionate Ownership Share	14.00%
Operating Leases, Rent Expense	$ 19,000,000	18,000,000	21,000,000
Leasing commitment, 2017	13,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	9,000,000
Leasing commitment, 2019	9,000,000
Leasing commitment, 2020	9,000,000
Leasing commitment, 2021 and thereafter	13,000,000
Operating leases, future minimum lease payments due	72,000,000
Long-term pollution control bonds	1,100,000,000	1,200,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	19,000,000
Alabama Power [Member] | Barges and Rail Cars [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating Leases, Rent Expense	13,000,000	14,000,000	18,000,000
Alabama Power [Member] | Residual Value, Leased Property [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Leasing commitment, 2017	0
Operating Leases, Future Minimum Payments, Due in Three Years	0
Leasing commitment, 2019	0
Leasing commitment, 2020	0
Leasing commitment, 2021 and thereafter	12,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	4,000,000
Georgia Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Capital Leases, Future Minimum Payments, Lesser Of Fair Value and Present Value	149,000,000
Fuel expense	2,033,000,000	2,547,000,000	2,307,000,000
Capacity Payments	10,000,000	19,000,000	27,000,000
Deferred capacity expense	203,000,000	167,000,000	162,000,000
Operating Leases, Rent Expense	$ 29,000,000	28,000,000	$ 32,000,000
Percentage Of Minimum Lease Payments	100.00%
Leasing commitment, 2017	$ 18,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	12,000,000
Leasing commitment, 2019	8,000,000
Leasing commitment, 2020	7,000,000
Leasing commitment, 2021 and thereafter	16,000,000
Operating leases, future minimum lease payments due	84,000,000
Long-term pollution control bonds	1,800,000,000	1,600,000,000
Senior Notes	$ 6,300,000,000	6,900,000,000
Period Of Service For Gas Transportation Supplier	1 year
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 43,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 23,000,000
Georgia Power [Member] | Plant McIntosh [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Period Of Service For Gas Transportation Supplier			15 years
Georgia Power [Member] | MEAG Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	5.00%
Georgia Power [Member] | Alabama Power [Member] | Payment Guarantee [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Long-term pollution control bonds	$ 25,000,000
Georgia Power [Member] | Alabama Power [Member] | Financial Guarantee [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Senior Notes	100,000,000
Georgia Power [Member] | Barges and Rail Cars [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Leasing commitment, 2017	10,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	5,000,000
Leasing commitment, 2019	1,000,000
Leasing commitment, 2020	1,000,000
Leasing commitment, 2021 and thereafter	3,000,000
Operating leases, future minimum lease payments due	35,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	15,000,000
Georgia Power [Member] | Residual Value, Leased Property [Member] | 2018 [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases, future minimum lease payments due	32,000,000
Gulf Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Fuel expense	445,000,000	605,000,000	$ 533,000,000
Expense Under Purchase Power Agreements Accounted For As Operating Leases	75,000,000	50,000,000	21,000,000
Deferred capacity expense	141,000,000	163,000,000
Operating Leases, Rent Expense	14,000,000	15,000,000	18,000,000
Leasing commitment, 2017	7,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	4,000,000
Operating leases, future minimum lease payments due	21,000,000
Long-term pollution control bonds	309,000,000	309,000,000
Senior Notes	1,010,000,000	1,070,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	10,000,000
Gulf Power [Member] | Barges and Rail Cars [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Leasing commitment, 2017	6,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	4,000,000
Operating leases, future minimum lease payments due	19,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	9,000,000
Gulf Power [Member] | Barges and Rail Cars [Member] | Plant Daniel [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Fuel cost recovery clause	2,000,000	3,000,000	3,000,000
Leasing commitment, 2017	1,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	1,000,000
Gulf Power [Member] | Barge Transportation [Member] | Plant Crist and Plant Smith [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Fuel cost recovery clause	10,000,000	10,000,000	12,000,000
Leasing commitment, 2017	5,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	5,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	5,000,000
Mississippi Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Fuel expense	$ 443,000,000	574,000,000	491,000,000
Term of Management Fee Contract	40 years
Management fee	$ 38,000,000
Operating Leases, Rent Expense	$ 5,000,000	10,000,000	10,000,000
Number of Railcars Used Under Operating Lease | Railcar	229
Company's share of the leases	50.00%
Fuel cost recovery clause	$ 2,000,000	3,000,000	3,000,000
Long-term pollution control bonds	83,000,000	83,000,000
Senior Notes	$ 1,100,000,000	1,100,000,000
Mississippi Power [Member] | Plant Daniel [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Company's share of the leases	50.00%
Mississippi Power [Member] | Plant Watson [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Company's share of the leases	100.00%
Mississippi Power [Member] | Barges and Rail Cars [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Average leasing commitment, 2015	$ 1,000,000
Average leasing commitment, 2016	0
Average leasing commitment, 2017	0
Mississippi Power [Member] | Fuel Handling Equipment [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating Leases, Rent Expense		200,000	200,000
Mississippi Power [Member] | Barge Transportation [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating Leases, Rent Expense	2,000,000	8,000,000	7,000,000
Southern Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Fuel expense	441,000,000	596,000,000	474,000,000
Operating Leases, Rent Expense	7,000,000	4,000,000	2,000,000
Leasing commitment, 2017	12,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	12,000,000
Leasing commitment, 2019	12,000,000
Leasing commitment, 2020	13,000,000
Leasing commitment, 2021 and thereafter	595,000,000
Senior Notes	2,700,000,000	1,600,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	11,000,000
Redeemable Put Option	43,000,000	$ 39,000,000	$ 29,000,000	$ 8,000,000
Non-Affiliate Operating Lease PPA [Member] | Georgia Power [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Biomass PPAs Amount	304,000,000
Leasing commitment, 2017	123,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	126,000,000
Leasing commitment, 2019	127,000,000
Leasing commitment, 2020	123,000,000
Leasing commitment, 2021 and thereafter	1,007,000,000
Operating leases, future minimum lease payments due	1,621,000,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 115,000,000