Consolidated Statements of Capitalization - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Maturity
Long-term debt payable to affiliated trusts	$ 206,000,000	$ 206,000,000
2017	0	2,019,000,000
2018	2,402,000,000	2,403,000,000
2019	3,074,000,000	3,076,000,000
2020	2,273,000,000	1,326,000,000
2021	2,643,000,000	2,655,000,000
2022	2,016,000,000	1,378,000,000
After Five Years	22,142,000,000	20,369,000,000
Total long-term senior notes and debt	36,820,000,000	35,247,000,000
Pollution control revenue bonds —
Total other long-term debt	10,987,000,000	9,404,000,000
Unamortized fair value adjustment of long-term debt	525,000,000	578,000,000
Capitalized lease obligations	204,000,000	136,000,000
Unamortized debt premium	44,000,000	52,000,000
Unamortized debt discount	(206,000,000)	(194,000,000)
Unamortized debt issuance expense	(226,000,000)	(213,000,000)
Total long-term debt (annual interest requirement — $1.8 billion)	48,354,000,000	45,216,000,000
Less amount due within one year	3,892,000,000	2,587,000,000
Long-term debt excluding amount due within one year	$ 44,462,000,000	$ 42,629,000,000
Percent capitalization	63.20%	61.30%
Cumulative preferred stock
Redeemable preferred stock	$ 324,000,000	$ 118,000,000
Total redeemable preferred stock - percent capitalization	0.50%	0.20%
Redeemable noncontrolling interests	$ 0	$ 164,000,000
Redeemable Noncontrolling Interest As Percent Of Capitalization	0.00%	0.20%
Common Stockholders' Equity:
Common stock	$ 5,038,000,000	$ 4,952,000,000
Paid-in capital	10,469,000,000	9,661,000,000
Treasury, at cost	(36,000,000)	(31,000,000)
Retained earnings	8,885,000,000	10,356,000,000
Accumulated other comprehensive loss	(189,000,000)	(180,000,000)
Total common stockholders' equity	$ 24,167,000,000	$ 24,758,000,000
Total common stockholders' equity - percent capitalization	34.40%	35.60%
Preferred and preference stock of subsidiaries	$ 1,361,000,000	$ 1,854,000,000
Total preferred and preference stock of subsidiaries - percent capitalization	1.90%	2.70%
Total stockholders' equity	$ 25,528,000,000	$ 26,612,000,000
Total capitalization	$ 70,314,000,000	$ 69,523,000,000
Percent capitalization	100.00%	100.00%
Redeemable Preferred Stock, $100 par or stated value \| Cumulative Preferred Stock
Cumulative preferred stock
Redeemable preferred stock	$ 324,000,000	$ 81,000,000
Redeemable Preferred Stock, $1 par value \| Cumulative Preferred Stock
Cumulative preferred stock
Redeemable preferred stock	0	37,000,000
Noncumulative Preferred Stock
Common Stockholders' Equity:
Preferred and preference stock of subsidiaries	0	45,000,000
Preference Stock, $1 par value
Common Stockholders' Equity:
Preferred and preference stock of subsidiaries	0	196,000,000
Preference Stock , $100 par or stated value
Common Stockholders' Equity:
Preferred and preference stock of subsidiaries	0	368,000,000
Redeemable Preferred Stock
Cumulative preferred stock
Redeemable preferred stock	324,000,000	118,000,000
Noncontrolling Interests
Common Stockholders' Equity:
Preferred and preference stock of subsidiaries	1,361,000,000	1,245,000,000
Adjustable Rate Loans
Maturity
2017	0	461,000,000
2018	1,420,000,000	1,520,000,000
2020	825,000,000	0
2021	25,000,000	25,000,000
After Five Years	0	15,000,000
Pollution control revenue bonds due 2019
Pollution control revenue bonds —
Long-term pollution control bonds	25,000,000	25,000,000
Maturity of Pollution Control Bonds Due 2022
Pollution control revenue bonds —
Long-term pollution control bonds	90,000,000	90,000,000
Pollution control revenue bonds due 2023 through 2049
Pollution control revenue bonds —
Long-term pollution control bonds	1,379,000,000	1,339,000,000
Maturity of Pollution Control Bonds Period Two
Pollution control revenue bonds —
Long-term pollution control bonds	1,680,000,000	1,721,000,000
Pollution control revenue bonds variable rate, Due 2018
Pollution control revenue bonds —
Long-term pollution control bonds	40,000,000	76,000,000
Pollution control revenue bonds variable rate due 2021
Pollution control revenue bonds —
Long-term pollution control bonds	65,000,000	65,000,000
Pollution control revenue bonds variable rate due 2022
Pollution control revenue bonds —
Long-term pollution control bonds	17,000,000	17,000,000
Plant Daniel revenue bonds (7.13%) due 2021
Pollution control revenue bonds —
Plant Daniel revenue bonds (7.13%) due 2021	270,000,000	270,000,000
Maturity Of FFB Loans Due 2020
Pollution control revenue bonds —
FFB loans	44,000,000	44,000,000
Maturity Of FFB Loans Due 2021
Pollution control revenue bonds —
FFB loans	44,000,000	44,000,000
Maturity Of Loans Due 2022
Pollution control revenue bonds —
FFB loans	44,000,000	44,000,000
Maturity Of FFB Bank Loans Due 2023 to 2053
Pollution control revenue bonds —
FFB loans	2,493,000,000	2,493,000,000
Maturity Of First Mortgage Bonds Due 2019
Pollution control revenue bonds —
First mortgage bonds	50,000,000	50,000,000
First Mortgage Bonds Due 2023 to 2057
Pollution control revenue bonds —
First mortgage bonds	975,000,000	575,000,000
Maturity Of Gas Facility Revenue Bonds Due 2022
Pollution control revenue bonds —
Gas facility revenue bonds	47,000,000	47,000,000
Maturity Of Gas Facility Revenue Bonds Due 2024 to 2033
Pollution control revenue bonds —
Gas facility revenue bonds	154,000,000	154,000,000
ALABAMA POWER CO
Maturity
Long-term debt payable to affiliated trusts	206,000,000	206,000,000
2017	0	525,000,000
2019	200,000,000	200,000,000
2020	250,000,000	250,000,000
2021	220,000,000	220,000,000
2022	750,000,000	200,000,000
After Five Years	4,975,000,000	4,425,000,000
Total long-term notes payable	6,420,000,000	5,845,000,000
Pollution control revenue bonds —
Long-term pollution control bonds	1,060,000,000	1,100,000,000
Total other long-term debt	1,060,000,000	1,096,000,000
Capitalized lease obligations	4,000,000	4,000,000
Unamortized debt (discount), net	(11,000,000)	(9,000,000)
Unamortized debt issuance expense	(51,000,000)	(46,000,000)
Total long-term debt (annual interest requirement — $1.8 billion)	7,628,000,000	7,096,000,000
Less amount due within one year	0	561,000,000
Long-term debt excluding amount due within one year	$ 7,628,000,000	$ 6,535,000,000
Percent capitalization	51.70%	49.70%
Cumulative preferred stock
Redeemable preferred stock	$ 291,000,000	$ 85,000,000
Total redeemable preferred stock - percent capitalization	2.00%	0.70%
Preferred stock	$ 291,000,000	$ 85,000,000
Preference stock	0	196,000,000
Common Stockholders' Equity:
Common stock	1,222,000,000	1,222,000,000
Paid-in capital	2,986,000,000	2,613,000,000
Retained earnings	2,647,000,000	2,518,000,000
Accumulated other comprehensive loss	(26,000,000)	(30,000,000)
Total common stockholders' equity	$ 6,829,000,000	$ 6,323,000,000
Total common stockholders' equity - percent capitalization	46.30%	48.10%
Total preferred and preference stock of subsidiaries - percent capitalization	0.00%	1.50%
Total stockholders' equity	$ 6,829,000,000	$ 6,323,000,000
Total capitalization	$ 14,748,000,000	$ 13,139,000,000
Percent capitalization	100.00%	100.00%
ALABAMA POWER CO \| Redeemable Preferred Stock, $100 par or stated value \| Cumulative Preferred Stock
Cumulative preferred stock
Redeemable preferred stock	$ 48,000,000	$ 48,000,000
ALABAMA POWER CO \| Redeemable Preferred Stock, $1 par value \| Cumulative Preferred Stock
Cumulative preferred stock
Redeemable preferred stock	243,000,000	37,000,000
ALABAMA POWER CO \| Adjustable Rate Loans
Maturity
2022	25,000,000	25,000,000
ALABAMA POWER CO \| Pollution control revenue bonds variable rate, Due 2018
Pollution control revenue bonds —
Long-term pollution control bonds	0	36,000,000
ALABAMA POWER CO \| Pollution control revenue bonds variable rate due 2021
Pollution control revenue bonds —
Long-term pollution control bonds	65,000,000	65,000,000
ALABAMA POWER CO \| Pollution control revenue bonds due 2034
Pollution control revenue bonds —
Long-term pollution control bonds	207,000,000	207,000,000
ALABAMA POWER CO \| Pollution Control Revenue Bonds Variable Rate Due 2024 - 2038
Pollution control revenue bonds —
Long-term pollution control bonds	788,000,000	788,000,000
GEORGIA POWER CO
Maturity
2017	0	450,000,000
2018	747,000,000	748,000,000
2019	499,000,000	500,000,000
2020	950,000,000	0
2021	325,000,000	325,000,000
2022	400,000,000	400,000,000
After Five Years	4,175,000,000	3,775,000,000
Total long-term notes payable	7,196,000,000	6,198,000,000
Pollution control revenue bonds —
Long-term pollution control bonds	1,800,000,000	1,800,000,000
Total other long-term debt	4,716,000,000	4,445,000,000
Capitalized lease obligations	154,000,000	169,000,000
Unamortized debt (discount), net	(12,000,000)	(10,000,000)
Unamortized debt issuance expense	(124,000,000)	(117,000,000)
Total long-term debt (annual interest requirement — $1.8 billion)	11,930,000,000	10,685,000,000
Less amount due within one year	857,000,000	460,000,000
Long-term debt excluding amount due within one year	$ 11,073,000,000	$ 10,225,000,000
Percent capitalization	48.10%	46.80%
Cumulative preferred stock
Preferred stock	$ 0	$ 45,000,000
Preference stock	0	221,000,000
Common Stockholders' Equity:
Common stock	398,000,000	398,000,000
Paid-in capital	7,328,000,000	6,885,000,000
Retained earnings	4,215,000,000	4,086,000,000
Accumulated other comprehensive loss	(10,000,000)	(13,000,000)
Total common stockholders' equity	$ 11,931,000,000	$ 11,356,000,000
Total common stockholders' equity - percent capitalization	51.90%	52.00%
Total preferred and preference stock of subsidiaries - percent capitalization	0.00%	1.20%
Total stockholders' equity	$ 11,931,000,000	$ 11,356,000,000
Total capitalization	$ 23,004,000,000	$ 21,847,000,000
Percent capitalization	100.00%	100.00%
GEORGIA POWER CO \| Noncumulative Preferred Stock
Cumulative preferred stock
Total preferred and preference stock	$ 0	$ 266,000,000
GEORGIA POWER CO \| Noncumulative Preferred Stock, $25 par value
Cumulative preferred stock
Preferred stock	0	45,000,000
GEORGIA POWER CO \| Noncumulative Preferred Stock, $100 par value
Cumulative preferred stock
Preference stock	0	221,000,000
GEORGIA POWER CO \| Adjustable Rate Loans
Maturity
2018	100,000,000	0
GEORGIA POWER CO \| Pollution control revenue bonds due 2023 through 2049
Pollution control revenue bonds —
Long-term pollution control bonds	53,000,000	53,000,000
GEORGIA POWER CO \| Maturity of Pollution Control Bonds Period Two
Pollution control revenue bonds —
Long-term pollution control bonds	940,000,000	900,000,000
GEORGIA POWER CO \| Maturity Of Pollution Control Bonds Variable Rate Due 2018
Pollution control revenue bonds —
Long-term pollution control bonds	13,000,000	13,000,000
GEORGIA POWER CO \| Maturity of Pollution Control Bonds Two Thousand Twenty Six to Two Thousand Fifty Three
Pollution control revenue bonds —
Long-term pollution control bonds	815,000,000	854,000,000
GEORGIA POWER CO \| Maturity Of FFB Loans Due 2020
Pollution control revenue bonds —
FFB loans	44,000,000	44,000,000
GEORGIA POWER CO \| Maturity Of FFB Loans Due 2021
Pollution control revenue bonds —
FFB loans	44,000,000	44,000,000
GEORGIA POWER CO \| Maturity Of Loans Due Two Thousand Twenty Two
Pollution control revenue bonds —
FFB loans	44,000,000	44,000,000
GEORGIA POWER CO \| Maturity Of FFB Bank Loans Due 2023 to 2053
Pollution control revenue bonds —
FFB loans	2,493,000,000	2,493,000,000
GEORGIA POWER CO \| Junior subordinated notes (5.00% to 6.25%) due 2057 to 2077
Pollution control revenue bonds —
Junior subordinated notes	270,000,000	0
GULF POWER CO
Maturity
2018	0
2019	0
2020	175,000,000	175,000,000
2021	0
2022	141,000,000
Total long-term notes payable	990,000,000	777,000,000
Pollution control revenue bonds —
Long-term pollution control bonds	309,000,000	309,000,000
Total other long-term debt	309,000,000	309,000,000
Unamortized debt (discount), net	(5,000,000)	(5,000,000)
Unamortized debt issuance expense	(9,000,000)	(7,000,000)
Total long-term debt (annual interest requirement — $1.8 billion)	1,285,000,000	1,074,000,000
Less amount due within one year	0	87,000,000
Long-term debt excluding amount due within one year	$ 1,285,000,000	$ 987,000,000
Percent capitalization	45.60%	39.10%
Cumulative preferred stock
Total redeemable preferred stock - percent capitalization	0.00%	5.80%
Preference stock	$ 0	$ 147,000,000
Common Stockholders' Equity:
Common stock	678,000,000	503,000,000
Paid-in capital	594,000,000	589,000,000
Retained earnings	259,000,000	296,000,000
Accumulated other comprehensive loss	0	1,000,000
Total common stockholders' equity	$ 1,531,000,000	$ 1,389,000,000
Total common stockholders' equity - percent capitalization	54.40%	55.10%
Total stockholders' equity	$ 1,531,000,000	$ 1,389,000,000
Total capitalization	$ 2,816,000,000	$ 2,523,000,000
Percent capitalization	100.00%	100.00%
GULF POWER CO \| 6% Preference stock
Cumulative preferred stock
Preference stock	$ 0	$ 54,000,000
GULF POWER CO \| 6.45 % Preference stock
Cumulative preferred stock
Preference stock	0	44,000,000
GULF POWER CO \| 5.6% Preference Stock
Cumulative preferred stock
Preference stock	0	49,000,000
GULF POWER CO \| Maturity of Long Term Senior Notes and Debt In Last Twelve Months
Maturity
2017	0	87,000,000
GULF POWER CO \| Maturity of Long Term Senior Notes and Debt in 2021
Maturity
2022	100,000,000	100,000,000
GULF POWER CO \| Maturity of Long Term Senior Notes and Debt Two Thousand Twenty Seven to Two Thousand Forty Four [Member]
Maturity
After Five Years	715,000,000	415,000,000
GULF POWER CO \| Maturity of Pollution Control Revenue Bonds 2023 through 2049
Pollution control revenue bonds —
Long-term pollution control bonds	190,000,000	190,000,000
GULF POWER CO \| Pollution control revenue bonds due 2023 through 2049
Pollution control revenue bonds —
Long-term pollution control bonds	37,000,000	37,000,000
GULF POWER CO \| Pollution control revenue bonds variable rate due 2022
Pollution control revenue bonds —
Long-term pollution control bonds	4,000,000	4,000,000
GULF POWER CO \| Pollution control revenue bonds due 2022-2042
Pollution control revenue bonds —
Long-term pollution control bonds	78,000,000	78,000,000
MISSISSIPPI POWER CO
Maturity
2017	0	35,000,000
2018	50,000,000	50,000,000
2019	125,000,000	125,000,000
After Five Years	630,000,000	630,000,000
Total long-term notes payable	1,705,000,000	2,040,000,000
Pollution control revenue bonds —
Long-term pollution control bonds	83,000,000	83,000,000
Total other long-term debt	353,000,000	904,000,000
Capitalized lease obligations	0	74,000,000
Unamortized debt premium	36,000,000	45,000,000
Unamortized debt discount	(1,000,000)	(2,000,000)
Unamortized debt issuance expense	(7,000,000)	(8,000,000)
Total long-term debt (annual interest requirement — $1.8 billion)	2,086,000,000	3,053,000,000
Less amount due within one year	989,000,000	629,000,000
Long-term debt excluding amount due within one year	$ 1,097,000,000	$ 2,424,000,000
Percent capitalization	44.10%	44.90%
Cumulative preferred stock
Total redeemable preferred stock - percent capitalization	1.30%	0.60%
Preferred stock	$ 33,000,000	$ 33,000,000
Common Stockholders' Equity:
Common stock	38,000,000	38,000,000
Paid-in capital	4,529,000,000	3,525,000,000
Retained earnings	(3,205,000,000)	(616,000,000)
Accumulated other comprehensive loss	(4,000,000)	(4,000,000)
Total common stockholders' equity	$ 1,358,000,000	$ 2,943,000,000
Total common stockholders' equity - percent capitalization	54.60%	54.50%
Total stockholders' equity	$ 1,358,000,000	$ 2,943,000,000
Total capitalization	$ 2,488,000,000	$ 5,400,000,000
Percent capitalization	100.00%	100.00%
MISSISSIPPI POWER CO \| Adjustable Rate Loans
Maturity
2018	$ 900,000,000	$ 1,200,000,000
MISSISSIPPI POWER CO \| Plant Daniel revenue bonds (7.13%) due 2021
Pollution control revenue bonds —
Plant Daniel revenue bonds (7.13%) due 2021	270,000,000	270,000,000
MISSISSIPPI POWER CO \| Pollution control revenue bonds due 2028
Pollution control revenue bonds —
Long-term pollution control bonds	43,000,000	43,000,000
MISSISSIPPI POWER CO \| Maturity Of Pollution Control Bonds 2017
Pollution control revenue bonds —
Long-term pollution control bonds	40,000,000	40,000,000
MISSISSIPPI POWER CO \| Maturity of Long-Term Debt Payable To Parent Company Period One
Pollution control revenue bonds —
Long-term debt due to parent company	0	551,000,000
SOUTHERN Co GAS
Maturity
2018	155,000,000
2019	350,000,000
2020	0
2021	330,000,000
2022	93,000,000
After Five Years	4,600,000,000
Total long-term notes payable		3,887,000,000
Pollution control revenue bonds —
Gas facility revenue bonds	200,000,000	200,000,000
Total other long-term debt	1,225,000,000	825,000,000
Unamortized fair value adjustment of long-term debt	525,000,000	578,000,000
Unamortized debt (discount), net	(17,000,000)	(9,000,000)
Total long-term debt (annual interest requirement — $1.8 billion)	6,048,000,000	5,281,000,000
Less amount due within one year	157,000,000	22,000,000
Long-term debt excluding amount due within one year	$ 5,891,000,000	$ 5,259,000,000
Percent capitalization	39.50%	36.60%
Cumulative preferred stock
Redeemable noncontrolling interests		$ 0
Common Stockholders' Equity:
Paid-in capital	$ 9,214,000,000	9,095,000,000
Retained earnings	(212,000,000)	(12,000,000)
Accumulated other comprehensive loss	20,000,000	26,000,000
Total common stockholders' equity	$ 9,022,000,000	$ 9,109,000,000
Total common stockholders' equity - percent capitalization	60.50%	63.40%
Total stockholders' equity	$ 9,022,000,000	$ 9,109,000,000
Total capitalization	$ 14,913,000,000	$ 14,368,000,000
Percent capitalization	100.00%	100.00%
SOUTHERN Co GAS \| Maturity of Long Term Senior Notes and Debt In Last Twelve Months
Maturity
2017	$ 0	$ 22,000,000
SOUTHERN Co GAS \| Maturity of Long Term Senior Notes and Debt 2018
Maturity
2018	155,000,000	155,000,000
SOUTHERN Co GAS \| Maturity of Long Term Senior Notes and Debt 2019
Maturity
2019	300,000,000	300,000,000
SOUTHERN Co GAS \| Maturity of Long Term Senior Notes and Debt in 2021
Maturity
2021	330,000,000	330,000,000
SOUTHERN Co GAS \| Maturity of Long Term Senior Notes and Debt 2022
Maturity
2022	46,000,000	46,000,000
SOUTHERN Co GAS \| Maturity of Long Term Senior Notes and Debt After Year Five
Maturity
After Five Years	3,484,000,000	3,034,000,000
SOUTHERN Co GAS \| Long Term Senior Notes
Maturity
Total long-term notes payable	4,315,000,000
SOUTHERN Co GAS \| First Mortgage Bonds Due 2019
Pollution control revenue bonds —
First mortgage bonds	50,000,000	50,000,000
SOUTHERN Co GAS \| First Mortgage Bonds Due 2023 to 2057
Pollution control revenue bonds —
First mortgage bonds	975,000,000	575,000,000
SOUTHERN Co GAS \| Maturity Of Gas Facility Revenue Bonds Due 2022
Pollution control revenue bonds —
Gas facility revenue bonds	47,000,000	47,000,000
SOUTHERN Co GAS \| Maturity Of Gas Facility Revenue Bonds Due 2024 to 2033
Pollution control revenue bonds —
Gas facility revenue bonds	$ 153,000,000	$ 153,000,000

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As a percent of total capitalization, the total of all Common Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity. This excludes temporary equity and preferred and preference stockholders' equity.

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First Mortgage Bonds

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Gas Facility Revenue Bonds

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Loan For Federal Financing Bank

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Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, plus capital lease obligations.

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Amount of long-term debt matured in the past twelve months following the date of the latest balance sheet presented in the financial statements, which may include maturities of long term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Long-term Notes and Other Long-term Debt with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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Long-term Debt Payable To Parent Company

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As a percent of total capitalization, the total of all Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest).

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Value of all nonredeemable preference stock (or preference stock redeemable solely at the option of the issuer) held by shareholders, which is net of related treasury stock. May be all or a portion of the number of preference shares authorized. These shares represent the ownership interest of the preference shareholders.

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.

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