Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Assets and liabilities measured at fair value on a recurring basis

As of December 31, 2017, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
As of December 31, 2017:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Assets:
Energy-related derivatives^(a)(b)	$	331	$	239	$	—	$	—	$	570
Interest rate derivatives	—		1		—		—		1
Foreign currency derivatives	—		129		—		—		129
Nuclear decommissioning trusts:^(c)
Domestic equity	690		82		—		—		772
Foreign equity	62		224		—		—		286
U.S. Treasury and government agency securities	—		251		—		—		251
Municipal bonds	—		68		—		—		68
Corporate bonds	21		315		—		—		336
Mortgage and asset backed securities	—		57		—		—		57
Private equity	—		—		—		29		29
Other	19		12		—		—		31
Cash equivalents	1,455		—		—		—		1,455
Other investments	9		—		1		—		10
Total	$	2,587	$	1,378	$	1	$	29	$	3,995
Liabilities:
Energy-related derivatives^(a)(b)	$	480	$	253	$	—	$	—	$	733
Interest rate derivatives	—		38		—		—		38
Foreign currency derivatives	—		23		—		—		23
Contingent consideration	—		—		22		—		22
Total	$	480	$	314	$	22	$	—	$	816


(a)	Energy-related derivatives exclude $11 million associated with premiums and certain weather derivatives accounted for based on intrinsic value rather than fair value.


(b)	Energy-related derivatives exclude cash collateral of $193 million.


(c)	Includes the investment securities pledged to creditors and collateral received, and excludes receivables related to investment income, pending investment sales, currencies, and payables related to pending investment purchases and the securities lending program. See Note 1 under "Nuclear Decommissioning" for additional information.

As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
As of December 31, 2016:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Assets:
Energy-related derivatives^(a)(b)	$	338	$	333	$	—	$	—	$	671
Interest rate derivatives	—		14		—		—		14
Nuclear decommissioning trusts:^(c)
Domestic equity	589		73		—		—		662
Foreign equity	48		168		—		—		216
U.S. Treasury and government agency securities	—		92		—		—		92
Municipal bonds	—		73		—		—		73
Corporate bonds	22		310		—		—		332
Mortgage and asset backed securities	—		183		—		—		183
Private equity	—		—		—		20		20
Other	11		15		—		—		26
Cash equivalents	1,172		—		—		—		1,172
Other investments	9		—		1		—		10
Total	$	2,189	$	1,261	$	1	$	20	$	3,471
Liabilities:
Energy-related derivatives^(a)(b)	$	345	$	285	$	—	$	—	$	630
Interest rate derivatives	—		29		—		—		29
Foreign currency derivatives	—		58		—		—		58
Contingent consideration	—		—		18		—		18
Total	$	345	$	372	$	18	$	—	$	735


(a)	Energy-related derivatives exclude $4 million associated with certain weather derivatives accounted for based on intrinsic value rather than fair value.


(b)	Energy-related derivatives exclude cash collateral of $62 million.


(c)	Includes the investment securities pledged to creditors and collateral received, and excludes receivables related to investment income, pending investment sales, currencies, and payables related to pending investment purchases and the securities lending program. See Note 1 under "Nuclear Decommissioning" for additional information.

Fair value measurements of investments calculated at net asset value per share as well as the nature and risk of those investments

As of December 31, 2017 and 2016, the fair value measurements of private equity investments held in the nuclear decommissioning trust that are calculated at net asset value per share (or its equivalent) as a practical expedient, as well as the nature and risks of those investments, were as follows:



	Fair Value		Unfunded Commitments		Redemption Frequency	Redemption Notice Period
	(in millions)
As of December 31, 2017	$	29	$	21	Not Applicable	Not Applicable
As of December 31, 2016	$	20	$	25	Not Applicable	Not Applicable

Financial instruments not having carrying amount equal to fair value

As of December 31, 2017 and 2016, other financial instruments for which the carrying amount did not equal fair value were as follows:



	Carrying Amount		Fair Value
	(in millions)
Long-term debt, including securities due within one year:
2017	$	48,151	$	51,348
2016	$	45,080	$	46,286

ALABAMA POWER CO

Fair Value Disclosures [Line Items]

Assets and liabilities measured at fair value on a recurring basis

As of December 31, 2017, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
As of December 31, 2017:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	4	$	—	$	—	$	4
Nuclear decommissioning trusts:^(*)
Domestic equity	442		81		—		—		523
Foreign equity	62		59		—		—		121
U.S. Treasury and government agency securities	—		24		—		—		24
Corporate bonds	21		160		—		—		181
Mortgage and asset backed securities	—		18		—		—		18
Private equity	—		—		—		29		29
Other	6		—		—		—		6
Cash equivalents	349		—		—		—		349
Total	$	880	$	346	$	—	$	29	$	1,255
Liabilities:
Energy-related derivatives	$	—	$	10	$	—	$	—	$	10


(*)	Excludes receivables related to investment income, pending investment sales, and payables related to pending investment purchases. See Note 1 under "Nuclear Decommissioning" for additional information.

As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
As of December 31, 2016:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	20	$	—	$	—	$	20
Nuclear decommissioning trusts:^(*)
Domestic equity	385		72		—		—		457
Foreign equity	48		47		—		—		95
U.S. Treasury and government agency securities	—		21		—		—		21
Corporate bonds	22		146		—		—		168
Mortgage and asset backed securities	—		19		—		—		19
Private equity	—		—		—		20		20
Other	—		10		—		—		10
Cash equivalents	262		—		—		—		262
Total	$	717	$	335	$	—	$	20	$	1,072
Liabilities:
Energy-related derivatives	$	—	$	9	$	—	$	—	$	9


(*)	Excludes receivables related to investment income, pending investment sales, and payables related to pending investment purchases. See Note 1 under "Nuclear Decommissioning" for additional information.

Fair value measurements of investments calculated at net asset value per share as well as the nature and risk of those investments

As of December 31, 2017 and 2016, the fair value measurements of private equity investments held in the nuclear decommissioning trusts that are calculated at net asset value per share (or its equivalent) as a practical expedient, as well as the nature and risks of those investments, were as follows:



	Fair Value		Unfunded Commitments		Redemption Frequency	Redemption Notice Period
	(in millions)
As of December 31, 2017	$	29	$	21	Not Applicable	Not Applicable
As of December 31, 2016	$	20	$	25	Not Applicable	Not Applicable

Financial instruments not having carrying amount equal to fair value

As of December 31, 2017 and 2016, other financial instruments for which the carrying amount did not equal fair value were as follows:



	Carrying Amount		Fair Value
	(in millions)
Long-term debt, including securities due within one year:
2017	$	7,625	$	8,305
2016	$	7,092	$	7,544

GEORGIA POWER CO

Fair Value Disclosures [Line Items]

Assets and liabilities measured at fair value on a recurring basis

As of December 31, 2017, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2017:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	6	$	—	$	6
Nuclear decommissioning trusts:^(*)
Domestic equity	248		1		—		249
Foreign equity	—		166		—		166
U.S. Treasury and government agency securities	—		227		—		227
Municipal bonds	—		68		—		68
Corporate bonds	—		155		—		155
Mortgage and asset backed securities	—		40		—		40
Other	12		12		—		24
Cash equivalents	690		—		—		690
Total	$	950	$	675	$	—	$	1,625
Liabilities:
Energy-related derivatives	$	—	$	19	$	—	$	19
Interest rate derivatives	—		5		—		5
Total	$	—	$	24	$	—	$	24


(*)	Includes the investment securities pledged to creditors and collateral received, and excludes receivables related to investment income, pending investment sales, currencies, and payables related to pending investment purchases and the securities lending program. See Note 1 under "Nuclear Decommissioning" for additional information.

As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2016:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	44	$	—	$	44
Interest rate derivatives	—		2		—		2
Nuclear decommissioning trusts:^(*)
Domestic equity	204		1		—		205
Foreign equity	—		121		—		121
U.S. Treasury and government agency securities	—		71		—		71
Municipal bonds	—		73		—		73
Corporate bonds	—		164		—		164
Mortgage and asset backed securities	—		164		—		164
Other	11		5		—		16
Total	$	215	$	645	$	—	$	860
Liabilities:
Energy-related derivatives	$	—	$	8	$	—	$	8
Interest rate derivatives	—		3		—		3
Total	$	—	$	11	$	—	$	11


(*)	Includes the investment securities pledged to creditors and collateral received, and excludes receivables related to investment income, pending investment sales, currencies, and payables related to pending investment purchases and the securities lending program. See Note 1 under "Nuclear Decommissioning" for additional information.

Financial instruments not having carrying amount equal to fair value

As of December 31, 2017 and 2016, other financial instruments for which the carrying amount did not equal fair value were as follows:



	Carrying Amount		Fair Value
	(in millions)
Long-term debt, including securities due within one year:
2017	$	11,777	$	12,531
2016	$	10,516	$	11,034

GULF POWER CO

Fair Value Disclosures [Line Items]

Assets and liabilities measured at fair value on a recurring basis

As of December 31, 2017, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2017:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Cash equivalents	$	21	$	—	$	—	$	21
Liabilities:
Energy-related derivatives	$	—	$	21	$	—	$	21

As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2016:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	5	$	—	$	5
Cash equivalents	20		—		—		20
Total	$	20	$	5	$	—	$	25
Liabilities:
Energy-related derivatives	$	—	$	29	$	—	$	29

Financial instruments not having carrying amount equal to fair value

As of December 31, 2017 and 2016, other financial instruments for which the carrying amount did not equal fair value were as follows:



	Carrying Amount		Fair Value
	(in millions)
Long-term debt:
2017	$	1,285	$	1,334
2016	$	1,074	$	1,097

MISSISSIPPI POWER CO

Fair Value Disclosures [Line Items]

Assets and liabilities measured at fair value on a recurring basis

As of December 31, 2017, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2017:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	2	$	—	$	2
Interest rate derivatives	—		1		—		1
Cash equivalents	224		—		—		224
Total	$	224	$	3	$	—	$	227
Liabilities:
Energy-related derivatives	$	—	$	9	$	—	$	9

As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2016:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	3	$	—	$	3
Interest rate derivatives	—		3		—		3
Cash equivalents	206		—		—		206
Total	$	206	$	6	$	—	$	212
Liabilities:
Energy-related derivatives	$	—	$	10	$	—	$	10

Financial instruments not having carrying amount equal to fair value

As of December 31, 2017 and 2016, other financial instruments for which the carrying amount did not equal fair value were as follows:



	Carrying Amount		Fair Value
	(in millions)
Long-term debt:
2017	$	2,086	$	2,076
2016	$	2,979	$	2,922

SOUTHERN POWER CO

Fair Value Disclosures [Line Items]

Assets and liabilities measured at fair value on a recurring basis

As of December 31, 2017, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2017:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	3	$	—	$	3
Foreign currency derivatives	—		129		—		129
Cash equivalents	21		—		—		21
Total	$	21	$	132	$	—	$	153
Liabilities:
Energy-related derivatives	$	—	$	13	$	—	$	13
Foreign currency derivatives	—		23		—		23
Contingent consideration	—		—		22		22
Total	$	—	$	36	$	22	$	58

As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
As of December 31, 2016:	(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
Assets:
Energy-related derivatives	$	—	$	21	$	—	$	21
Interest rate derivatives	—		1		—		1
Cash equivalents	628		—		—		628
Total	$	628	$	22	$	—	$	650
Liabilities:
Energy-related derivatives	$	—	$	5	$	—	$	5
Foreign currency derivatives	—		58		—		58
Contingent consideration	—		—		18		18
Total	$	—	$	63	$	18	$	81

Financial instruments not having carrying amount equal to fair value

As of December 31, 2017 and 2016, other financial instruments for which the carrying amount did not equal fair value were as follows:



	Carrying Amount		Fair Value
	(in millions)
Long-term debt, including securities due within one year:
2017	$	5,841	$	6,079
2016	$	5,628	$	5,691

SOUTHERN Co GAS

Fair Value Disclosures [Line Items]

Assets and liabilities measured at fair value on a recurring basis

As of December 31, 2017, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
As of December 31, 2017:	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Net Asset Value as a Practical Expedient (NAV)		Total
	(in millions)
Assets:
Energy-related derivatives^(a)(b)	$	331	$	223	$	—	$	—	$	554
Liabilities:
Energy-related derivatives^(a)(b)	$	479	$	181	$	—	$	—	$	660


(a)	Energy-related derivatives excludes $11 million associated with premiums and certain weather derivatives accounted for based on intrinsic value rather than fair value.


(b)	Energy-related derivatives excludes cash collateral of $193 million.

As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:



	Fair Value Measurements Using
As of December 31, 2016:	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Net Asset Value as a Practical Expedient (NAV)		Total
	(in millions)
Assets:
Energy-related derivatives^(a)(b)	$	338	$	239	$	—	$	—	$	577
Liabilities:
Energy-related derivatives^(a)(b)	$	345	$	224	$	—	$	—	$	569


(a)	Energy-related derivatives excludes $4 million associated with certain weather derivatives accounted for based on intrinsic value rather than fair value.


(b)	Energy-related derivatives excludes cash collateral of $62 million.

Financial instruments not having carrying amount equal to fair value

The following table presents the carrying amount and fair value of the Company's long-term debt as of December 31:



	Carrying Amount		Fair Value
	(in millions)
Long-term debt, including securities due within one year:
2017	$	6,048	$	6,471
2016	$	5,281	$	5,491