Financing (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Line Items]

Scheduled maturities and redemptions of securities due within one year

A summary of scheduled maturities of securities due within one year at December 31 was as follows:

	2017			2016
	(in millions)
Senior notes	$	2,354		$	1,995
Other long-term debt	1,420			485
Revenue bonds(*)	90			76
Capitalized leases	31			32
Unamortized debt issuance expense/discount	(3		)	(1		)
Total	$	3,892		$	2,587

(*) Includes $50 million in revenue bonds classified as short term at December 31, 2017 that were remarketed in an index rate mode subsequent to December 31, 2017. Also includes $40 million in pollution control revenue bonds classified as short term since they are variable rate demand obligations supported by short-term credit facilities; however, the final maturity dates range from 2020 to 2028.

Temporary Equity

The following table presents changes during the year in redeemable preferred stock of subsidiaries for Southern Company:

	Redeemable Preferred Stock of Subsidiaries
	(in millions)
Balance at December 31, 2014	$	375
Issued	—
Redeemed	(262		)
Issuance costs	5
Balance at December 31, 2015:	118
Issued	—
Redeemed	—
Balance at December 31, 2016:	118
Issued	250
Redeemed	(38		)
Issuance costs	(6		)
Balance at December 31, 2017:	$	324

Credit arrangements with banks

At December 31, 2017, committed credit arrangements with banks were as follows:

	Expires												Executable Term Loans				Expires Within One Year
Company	2018		2019		2020		2022		Total		Unused		One Year		Two Years		Term Out		No Term Out
	(in millions)
Southern Company(a)	$	—	$	—	$	—	$	2,000	$	2,000	$	1,999	$	—	$	—	$	—	$	—
Alabama Power	35		—		500		800		1,335		1,335		—		—		—		35
Georgia Power	—		—		—		1,750		1,750		1,732		—		—		—		—
Gulf Power	30		25		225		—		280		280		45		—		20		10
Mississippi Power	100		—		—		—		100		100		—		—		—		100
Southern Power Company(b)	—		—		—		750		750		728		—		—		—		—
Southern Company Gas(c)	—		—		—		1,900		1,900		1,890		—		—		—		—
Other	30		—		—		—		30		30		20		—		20		10
Southern Company Consolidated	$	195	$	25	$	725	$	7,200	$	8,145	$	8,094	$	65	$	—	$	40	$	155

(a) Represents the Southern Company parent entity.

(b) Does not include Southern Power's $120 million continuing letter of credit facility for standby letters of credit expiring in 2019, of which $19 million remains unused at December 31, 2017.

(c) Southern Company Gas, as the parent entity, guarantees the obligations of Southern Company Gas Capital, which is the borrower of $1.4 billion of these arrangements. Southern Company Gas' committed credit arrangements also include $500 million for which Nicor Gas is the borrower and which is restricted for working capital needs of Nicor Gas.

Short-term borrowings

Details of short-term borrowings were as follows:

	Short-term Debt at the End of the Period
	Amount Outstanding		Weighted Average Interest Rate
	(in millions)
December 31, 2017:
Commercial paper	$	1,832	1.8	%
Short-term bank debt	607		2.3	%
Total	$	2,439	1.9	%
December 31, 2016:
Commercial paper	$	1,909	1.1	%
Short-term bank debt	123		1.7	%
Total	$	2,032	1.1	%

ALABAMA POWER CO

Debt Disclosure [Line Items]

Credit arrangements with banks

At December 31, 2017, committed credit arrangements with banks were as follows:

Expires										Expires Within One Year
2018		2020		2022		Total		Unused		Term Out		No Term Out
(in millions)						(in millions)				(in millions)
$	35	$	500	$	800	$	1,335	$	1,335	$	—	$	35

GEORGIA POWER CO

Debt Disclosure [Line Items]

Scheduled maturities and redemptions of securities due within one year

A summary of scheduled maturities of securities due within one year at December 31 was as follows:

	2017			2016
	(in millions)
Senior notes	$	750		$	450
Capital leases	11			10
Other long-term debt	100			—
Unamortized debt issuance expense	(1		)	—
Total	$	860		$	460

Short-term borrowings

Details of short-term borrowings outstanding were as follows:

	Short-term Debt at the End of the Period
	Amount Outstanding		Weighted Average Interest Rate
	(in millions)
December 31, 2017:
Short-term bank debt	$	150	2.2	%
December 31, 2016:
Commercial paper	$	392	1.1	%

GULF POWER CO

Debt Disclosure [Line Items]

Credit arrangements with banks

At December 31, 2017, committed credit arrangements with banks were as follows:

Expires										Executable Term Loans				Expires Within One Year
2018		2019		2020		Total		Unused		One Year		Two Years		Term Out		No Term Out
(in millions)						(in millions)				(in millions)				(in millions)
$	30	$	25	$	225	$	280	$	280	$	45	$	—	$	20	$	10

Short-term borrowings

Details of short-term borrowings were as follows:

	Short-term Debt at the End of the Period
	Amount Outstanding		Weighted Average Interest Rate
	(in millions)
December 31, 2017:
Commercial paper	$	45	2.0%
December 31, 2016:
Commercial paper	$	168	1.1%
Short-term bank debt	100		1.5%
Total	$	268	1.2%

MISSISSIPPI POWER CO

Debt Disclosure [Line Items]

Scheduled maturities and redemptions of securities due within one year

A summary of scheduled maturities and redemptions of securities due within one year at December 31, 2017 and 2016 was as follows:

	2017			2016
	(in millions)
Parent company loans	$	—		$	551
Senior notes	—			35
Bank term loans	900			—
Revenue bonds(*)	90			40
Capitalized leases	—			3
Unamortized debt issuance expense	(1		)	—
Outstanding at December 31	$	989		$	629

(*) Includes $50 million in revenue bonds classified as short term at December 31, 2017 that were remarketed in an index rate mode subsequent to December 31, 2017. Also includes $40 million in pollution control revenue bonds classified as short term since they are variable rate demand obligations supported by short-term credit facilities; however, the final maturity dates range from 2020 to 2028.

Credit arrangements with banks

At December 31, 2017, committed credit arrangements with banks were as follows:

Expires			Executable Term Loans		Expires Within One Year
2018	Total	Unused	One Year	Two Years	Term Out	No Term Out
(in millions)	(in millions)		(in millions)		(in millions)
$100	$100	$100	$—	$—	$—	$100

SOUTHERN POWER CO

Debt Disclosure [Line Items]

Scheduled maturities and redemptions of securities due within one year

Maturities of long-term debt for the next five years are as follows:

	December 31, 2017
	(in millions)
2018	$	770
2019	600
2020	825
2021	300
2022(*)	677

(*) Represents euro-denominated debt at the U.S. dollar denominated hedge settlement amount.

Short-term borrowings

Commercial paper is included in notes payable in the consolidated balance sheets as noted below:

	Commercial Paper at the End of the Period
	Amount Outstanding		Weighted Average Interest Rate
	(in millions)
December 31, 2017	$	105	2.0	%
December 31, 2016	$	—	N/A

SOUTHERN Co GAS

Debt Disclosure [Line Items]

Temporary Equity

The roll-forwards of the redeemable noncontrolling interest for the successor period of July 1, 2016 through December 31, 2016 and the predecessor period of January 1, 2016 through June 30, 2016 are detailed below:

Predecessor –	(in millions)
Balance at December 31, 2015	$	—
Reclassification of noncontrolling interest to contingently redeemable noncontrolling interest	46
Net income attributable to noncontrolling interest	14
Distribution to noncontrolling interest	(19		)
Balance at June 30, 2016	$	41
Successor –	(in millions)
Balance at July 1, 2016	$	174
Reclassification of contingently redeemable noncontrolling interest to mandatorily redeemable noncontrolling interest	(174		)
Balance at December 31, 2016	$	—

Credit arrangements with banks

At December 31, 2017, committed credit arrangements with banks were as follows:

Company	Expires 2022		Unused
	(in millions)
Southern Company Gas Capital	$	1,400	$	1,390
Nicor Gas	500		500
Total	$	1,900	$	1,890

Short-term borrowings

Details of commercial paper borrowings outstanding were as follows:

	Short-term Debt at the End of the Period
	Amount Outstanding		Weighted Average Interest Rate
	(in millions)
December 31, 2017:
Southern Company Gas Capital	$	1,243	1.73	%
Nicor Gas	275		1.83
Total	$	1,518	1.75	%
December 31, 2016:
Southern Company Gas Capital	$	733	1.09	%
Nicor Gas	524		0.95
Total	$	1,257	1.03	%

Redeemable Preferred Stock | ALABAMA POWER CO

Debt Disclosure [Line Items]

Temporary Equity

Information for each outstanding series is in the table below:

Preferred/Preference Stock	Par Value/Stated Capital Per Share	Shares Outstanding	Redemption Price Per Share
4.92% Preferred Stock	$100	80,000	$103.23
4.72% Preferred Stock	$100	50,000	$102.18
4.64% Preferred Stock	$100	60,000	$103.14
4.60% Preferred Stock	$100	100,000	$104.20
4.52% Preferred Stock	$100	50,000	$102.93
4.20% Preferred Stock	$100	135,115	$105.00
5.00% Class A Preferred Stock	$25	10,000,000	Stated Capital(*)

(*) Prior to October 1, 2022: $25.50; on or after October 1, 2022: Stated Capital

Redeemable Preferred Stock | MISSISSIPPI POWER CO

Debt Disclosure [Line Items]

Temporary Equity

Information for each outstanding series is in the table below:

Preferred Stock	Par Value/Stated Capital Per Share		Shares Outstanding	Redemption Price Per Share
4.40% Preferred Stock	$	100	8,867	$	104.32
4.60% Preferred Stock	$	100	8,643	$	107.00
4.72% Preferred Stock	$	100	16,700	$	102.25
5.25% Preferred Stock(*)	$	100	300,000	$	100.00

(*) There are 1,200,000 outstanding depositary shares, each representing one-fourth of a share of the 5.25% preferred stock.