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This element represents the total consolidated (as applicable) capitalization of the entity which is comprised of its long-term debt and equity instruments. The table may be detailed by subsidiary (legal entity) and include information by type of debt or equity detailed by instrument.

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Face amount or stated value per share of common stock.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount (premium).

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Capitalization (Details) - USD ($)	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Total long -term senior notes and debt	$ 35,247,000,000		$ 20,418,000,000
2017	2,019,000,000		1,995,000,000
2018	2,353,000,000		1,697,000,000
2019	3,076,000,000		1,176,000,000
2021	2,655,000,000		200,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five	21,797,000,000		$ 10,972,000,000
Annualized Interest Long Term Debt	$ 1,600,000,000
Common stock, par value per share (in dollars per share)	$ 5		$ 5
Common Stock, Shares Authorized	1,500,000,000		1,500,000,000
Treasury shares	800,000		3,400,000
Other Long-term Debt	$ 9,404,000,000		$ 6,808,000,000
Unamortized Fair Value Adjustment of Long-term Debt	578,000,000		0
Long Term Debt and Capital Lease Obligation Net	45,216,000,000		27,362,000,000
Long-term Debt and Capital Lease Obligations, Current	2,587,000,000		2,674,000,000
Long-term Debt and Capital Lease Obligations	$ 42,629,000,000		$ 24,688,000,000
Percent capitalization	61.30%		52.60%
Treasury Stock, Value	$ (31,000,000)		$ (142,000,000)
Additional Paid in Capital, Common Stock	9,661,000,000		6,282,000,000
Retained Earnings (Accumulated Deficit)	10,356,000,000		10,010,000,000
Accumulated OCI	(180,000,000)		(130,000,000)
Common Stockholders' Equity	$ 24,758,000,000		$ 20,592,000,000
Total common stockholders' equity - percent capitalization	35.60%		44.00%
Noncontrolling interests	$ 1,854,000,000		$ 1,390,000,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	26,612,000,000		21,982,000,000	$ 20,926,000,000	$ 19,764,000,000
Total Capitalization	$ 69,523,000,000		$ 46,831,000,000
Capitalization in Percent	100.00%		100.00%
Maturity of Long Term Senior Notes and Debt in Year Five [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.35%		2.35%
Maturity of Long Term Senior Notes and Debt in Year Five [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	9.10%		9.10%
Maturity Of First Mortgage Bonds Due Two Thousand Seventeen [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.30%		1.30%
Maturity Of First Mortgage Bonds Due Two Thousand Seventeen [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.20%		7.20%
Maturity of Long Term Senior Notes and Debt in Year Two [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.50%		1.50%
Maturity of Long Term Senior Notes and Debt in Year Two [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.40%		5.40%
Maturity of Long Term Senior Notes and Debt in Year Three [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.85%		1.85%
Maturity of Long Term Senior Notes and Debt in Year Three [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.55%		5.55%
Maturity Of Gas Facility Revenue Bonds Due 2022 to 2033 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.28%
Maturity Of First Mortgage Bonds Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.70%
First Mortgage Bonds	$ 50,000,000		$ 0
Maturity Of First Mortgage Bonds Due Two Thousand Twenty Three To Two Thousand Thirty Eight [Member]
Debt Instrument [Line Items]
First Mortgage Bonds	575,000,000		0
Maturity Of Gas Facility Revenue Bonds Due Two Thousand Twenty Two To Two Thousand Thirty Eight [Member]
Debt Instrument [Line Items]
Gas Facility Revenue Bonds	200,000,000		$ 0
Predecessor [Member]
Debt Instrument [Line Items]
Percent capitalization			45.20%
Total common stockholders' equity - percent capitalization			54.20%
Noncontrolling Interest in Percent of Capitalization			0.60%
Capitalization in Percent			100.00%
Southern Company Gas [Member]
Debt Instrument [Line Items]
2017	22,000,000
2018	155,000,000
2019	350,000,000
2021	330,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five	3,900,000,000
First Mortgage Bonds	625,000,000		$ 375,000,000
Gas Facility Revenue Bonds	$ 200,000,000		$ 200,000,000
Southern Company Gas [Member] \| Maturity of Long Term Senior Notes and Debt in Year Five [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.50%
Southern Company Gas [Member] \| Maturity of Long Term Senior Notes and Debt in Year Five [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	9.10%
Southern Company Gas [Member] \| Maturity Of First Mortgage Bonds Due Two Thousand Seventeen [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.20%
Southern Company Gas [Member] \| Maturity of Long Term Senior Notes and Debt in Year Two [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.50%
Southern Company Gas [Member] \| Maturity of Long Term Senior Notes and Debt in Year Three [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.25%
Southern Company Gas [Member] \| Notes Payable Due 2016-2046 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.47%		1.47%
Southern Company Gas [Member] \| Notes Payable Due 2016-2046 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	9.10%		9.10%
Southern Company Gas [Member] \| Maturity Of Senior Notes And Debt in Two Thousand Twenty Two to Two Thousand Forty Six [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.45%
Southern Company Gas [Member] \| Maturity Of Senior Notes And Debt in Two Thousand Twenty Two to Two Thousand Forty Six [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.70%
Southern Company Gas [Member] \| Maturity Of First Mortgage Bonds Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.70%
Southern Company Gas [Member] \| Maturity Of First Mortgage Bonds Due Two Thousand Twenty Three To Two Thousand Thirty Eight [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.66%
Southern Company Gas [Member] \| Maturity Of First Mortgage Bonds Due Two Thousand Twenty Three To Two Thousand Thirty Eight [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.58%
Southern Company Gas [Member] \| Successor [Member]
Debt Instrument [Line Items]
2017	$ 22,000,000
2018	155,000,000
2019	300,000,000
2021	330,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five	3,100,000,000
First Mortgage Bonds	625,000,000
Annualized Interest Long Term Debt	$ 207,000,000
Common stock, par value per share (in dollars per share)	$ 0.01
Common Stock, Shares Authorized	100,000,000
Common Stock, Shares, Outstanding	100
Treasury shares	0
Other Long-term Debt	$ 825,000,000
Unamortized Fair Value Adjustment of Long-term Debt	578,000,000
Debt Instrument, Unamortized Discount (Premium), Net	9,000,000
Long Term Debt and Capital Lease Obligation Net	5,281,000,000
Long-term Debt and Capital Lease Obligations, Current	22,000,000
Long-term Debt and Capital Lease Obligations	$ 5,259,000,000
Percent capitalization	36.60%
Treasury Stock, Value	$ 0
Additional Paid in Capital, Common Stock	9,095,000,000
Retained Earnings (Accumulated Deficit)	(12,000,000)
Accumulated OCI	26,000,000
Common Stockholders' Equity	$ 9,109,000,000
Total common stockholders' equity - percent capitalization	63.40%
Noncontrolling Interest in Percent of Capitalization	0.00%
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 9,109,000,000	$ 8,001,000,000
Total Capitalization	$ 14,368,000,000
Capitalization in Percent	100.00%
Southern Company Gas [Member] \| Successor [Member] \| Notes Payable Due 2016-2046 [Member]
Debt Instrument [Line Items]
Total long -term senior notes and debt	$ 3,887,000,000
Southern Company Gas [Member] \| Successor [Member] \| Maturity Of Gas Facility Revenue Bonds Due 2022 to 2033 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.28%		1.28%
Southern Company Gas [Member] \| Successor [Member] \| Maturity Of First Mortgage Bonds Due 2019 [Member]
Debt Instrument [Line Items]
First Mortgage Bonds	$ 50,000,000
Southern Company Gas [Member] \| Successor [Member] \| Maturity Of First Mortgage Bonds Due Two Thousand Twenty Three To Two Thousand Thirty Eight [Member]
Debt Instrument [Line Items]
First Mortgage Bonds	575,000,000
Southern Company Gas [Member] \| Successor [Member] \| Maturity Of Gas Facility Revenue Bonds Due Two Thousand Twenty Two To Two Thousand Thirty Eight [Member]
Debt Instrument [Line Items]
Gas Facility Revenue Bonds	200,000,000
Southern Company Gas [Member] \| Predecessor [Member]
Debt Instrument [Line Items]
Total long -term senior notes and debt			$ 3,181,000,000
First Mortgage Bonds			$ 375,000,000
Common stock, par value per share (in dollars per share)			$ 5
Common Stock, Shares Authorized			750,000,000
Common Stock, Shares, Outstanding			120,400,000
Treasury shares			200,000.0
Other Long-term Debt			$ 575,000,000
Unamortized Fair Value Adjustment of Long-term Debt			68,000,000
Debt Instrument, Unamortized Discount (Premium), Net			4,000,000
Long Term Debt and Capital Lease Obligation Net			3,820,000,000
Long-term Debt and Capital Lease Obligations, Current			545,000,000
Long-term Debt and Capital Lease Obligations			3,275,000,000
Treasury Stock, Value			(8,000,000)
Additional Paid in Capital, Common Stock			2,702,000,000
Retained Earnings (Accumulated Deficit)			1,421,000,000
Accumulated OCI			(186,000,000)
Common Stockholders' Equity			3,929,000,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ 3,933,000,000	3,975,000,000	$ 3,828,000,000	$ 3,613,000,000
Total Capitalization			7,250,000,000
Southern Company Gas [Member] \| Predecessor [Member] \| Maturity Of Gas Facility Revenue Bonds Due Two Thousand Twenty Two To Two Thousand Thirty Eight [Member]
Debt Instrument [Line Items]
Gas Facility Revenue Bonds			200,000,000
Noncontrolling Interest [Member]
Debt Instrument [Line Items]
Noncontrolling interests	1,245,000,000		781,000,000
Noncontrolling Interest [Member] \| Southern Company Gas [Member] \| Successor [Member]
Debt Instrument [Line Items]
Noncontrolling interests	$ 0
Noncontrolling Interest [Member] \| Southern Company Gas [Member] \| Predecessor [Member]
Debt Instrument [Line Items]
Noncontrolling interests			$ 46,000,000