Retirement Benefits (Details) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in next fiscal year				$ 0
Amortization:
Defined Benefit Plan, Contributions by Employer	$ 125,000,000
Pension Plans [Member] \| Southern Company [Member]
Pension Plans and Postretirement Plans
Service cost		$ 68,000,000	$ 65,000,000	192,000,000	$ 193,000,000
Interest cost		110,000,000	111,000,000	311,000,000	333,000,000
Expected return on plan assets		(203,000,000)	(181,000,000)	(577,000,000)	(543,000,000)
Amortization:
Prior service costs		3,000,000	6,000,000	10,000,000	19,000,000
Net (gain)/loss		45,000,000	53,000,000	120,000,000	161,000,000
Net periodic pension cost		23,000,000	54,000,000	56,000,000	163,000,000
Pension Plans [Member] \| Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost		14,000,000	14,000,000	43,000,000	44,000,000
Interest cost		23,000,000	26,000,000	71,000,000	79,000,000
Expected return on plan assets		(46,000,000)	(44,000,000)	(138,000,000)	(133,000,000)
Amortization:
Prior service costs		1,000,000	2,000,000	2,000,000	5,000,000
Net (gain)/loss		10,000,000	14,000,000	30,000,000	41,000,000
Net periodic pension cost		2,000,000	12,000,000	8,000,000	36,000,000
Pension Plans [Member] \| Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost		17,000,000	18,000,000	52,000,000	54,000,000
Interest cost		34,000,000	38,000,000	102,000,000	115,000,000
Expected return on plan assets		(64,000,000)	(62,000,000)	(193,000,000)	(188,000,000)
Amortization:
Prior service costs		1,000,000	2,000,000	4,000,000	7,000,000
Net (gain)/loss		14,000,000	19,000,000	41,000,000	57,000,000
Net periodic pension cost		2,000,000	15,000,000	6,000,000	45,000,000
Pension Plans [Member] \| Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost		3,000,000	3,000,000	9,000,000	9,000,000
Interest cost		5,000,000	5,000,000	14,000,000	15,000,000
Expected return on plan assets		(9,000,000)	(8,000,000)	(26,000,000)	(24,000,000)
Amortization:
Prior service costs		0	1,000,000	1,000,000	1,000,000
Net (gain)/loss		2,000,000	2,000,000	5,000,000	7,000,000
Net periodic pension cost		1,000,000	3,000,000	3,000,000	8,000,000
Pension Plans [Member] \| Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost		3,000,000	3,000,000	9,000,000	9,000,000
Interest cost		4,000,000	5,000,000	14,000,000	16,000,000
Expected return on plan assets		(9,000,000)	(8,000,000)	(26,000,000)	(25,000,000)
Amortization:
Prior service costs		1,000,000	0	1,000,000	1,000,000
Net (gain)/loss		2,000,000	3,000,000	5,000,000	8,000,000
Net periodic pension cost		1,000,000	3,000,000	3,000,000	9,000,000
Other Postretirement Benefits [Member] \| Southern Company [Member]
Pension Plans and Postretirement Plans
Service cost		6,000,000	6,000,000	17,000,000	17,000,000
Interest cost		20,000,000	20,000,000	55,000,000	59,000,000
Expected return on plan assets		(16,000,000)	(15,000,000)	(44,000,000)	(44,000,000)
Amortization:
Prior service costs		1,000,000	1,000,000	4,000,000	3,000,000
Net (gain)/loss		5,000,000	4,000,000	12,000,000	13,000,000
Net periodic pension cost		16,000,000	16,000,000	44,000,000	48,000,000
Other Postretirement Benefits [Member] \| Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost		1,000,000	1,000,000	4,000,000	4,000,000
Interest cost		5,000,000	5,000,000	14,000,000	15,000,000
Expected return on plan assets		(6,000,000)	(6,000,000)	(19,000,000)	(19,000,000)
Amortization:
Prior service costs		1,000,000	2,000,000	3,000,000	3,000,000
Net (gain)/loss		0	0	1,000,000	1,000,000
Net periodic pension cost		1,000,000	2,000,000	3,000,000	4,000,000
Other Postretirement Benefits [Member] \| Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost		2,000,000	2,000,000	5,000,000	5,000,000
Interest cost		7,000,000	9,000,000	22,000,000	26,000,000
Expected return on plan assets		(6,000,000)	(6,000,000)	(17,000,000)	(18,000,000)
Amortization:
Prior service costs		0	0	1,000,000	0
Net (gain)/loss		3,000,000	2,000,000	7,000,000	8,000,000
Net periodic pension cost		6,000,000	7,000,000	18,000,000	21,000,000
Other Postretirement Benefits [Member] \| Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost		0	1,000,000	1,000,000	1,000,000
Interest cost		1,000,000	0	2,000,000	2,000,000
Expected return on plan assets		0	0	(1,000,000)	(1,000,000)
Amortization:
Prior service costs		0	0	0	0
Net (gain)/loss		0	0	0	0
Net periodic pension cost		1,000,000	1,000,000	2,000,000	2,000,000
Other Postretirement Benefits [Member] \| Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost		0	0	1,000,000	1,000,000
Interest cost		0	1,000,000	2,000,000	3,000,000
Expected return on plan assets		0	0	(1,000,000)	(1,000,000)
Amortization:
Prior service costs		0	0	0	0
Net (gain)/loss		1,000,000	0	1,000,000	0
Net periodic pension cost		$ 1,000,000	$ 1,000,000	$ 3,000,000	$ 3,000,000

Defined Benefit Plan, Net Periodic Benefit Cost, Amortization [Abstract]

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The amount of gains or losses recognized in net periodic benefit cost.

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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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- Definition

Amount of contributions made by the employer to defined benefit plans.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

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