Debt Instrument, Remaining Maturity Term

No definition available.

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- Definition

Derivative, Settlement, Notional Amount

+ References

No definition available.

+ Details

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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- Definition

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

+ References

+ Details

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Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

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

+ References

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

The effective portion of losses on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

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- Definition

The cash outflow from the repayment of a long-term debt instrument issued, secured by a first mortgage deed of trust, containing a pledge of real property. The lender has the highest claim on the property in case of default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3291-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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Balance Type:	credit
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- Definition

The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3291-108585

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Debt and Credit Facilities (Details)						6 Months Ended
Debt and Credit Facilities (Details)	Jul. 15, 2016 USD ($)	May 15, 2016 USD ($)	May 13, 2016 USD ($)	Feb. 01, 2016 USD ($)	Jan. 23, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 23, 2016 USD ($)	May 31, 2016 USD ($)	May 18, 2016 USD ($)	Dec. 31, 2015 USD ($)	Nov. 30, 2015 USD ($)
Debt Instrument [Line Items]
Repayments of senior notes						$ 125,000,000	$ 200,000,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Outstanding						$ 114,000,000	$ 459,000,000				$ 1,010,000,000
Remaining maturity term						1 day
Southern Gas Company Capital [Member]
Debt Instrument [Line Items]
Ratio of total debt to total capitalization, no more than (as a percent)						0.52	0.49				0.54
Southern Gas Company Capital [Member] \| Commercial Paper [Member]
Debt Instrument [Line Items]
Effective interest rate (as a percent)						0.70%
Outstanding						$ 20,000,000	$ 269,000,000				$ 471,000,000
Nicor Gas [Member]
Debt Instrument [Line Items]
Ratio of total debt to total capitalization, no more than (as a percent)						0.45	0.49				0.56
Nicor Gas [Member] \| Commercial Paper [Member]
Debt Instrument [Line Items]
Effective interest rate (as a percent)						0.50%
Outstanding						$ 94,000,000	$ 190,000,000				$ 539,000,000
Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Loss on settlement of derivative			$ 26,000,000
Minimum [Member] \| Commercial Paper [Member]
Debt Instrument [Line Items]
Debt term						1 day
Maximum [Member]
Debt Instrument [Line Items]
Ratio of total debt to total capitalization, no more than (as a percent)						0.7
Maximum [Member] \| Commercial Paper [Member]
Debt Instrument [Line Items]
Debt term						59 days
Callable Debt [Member]
Debt Instrument [Line Items]
Outstanding						$ 275,000,000
Senior Notes [Member] \| Southern Gas Company Capital [Member]
Debt Instrument [Line Items]
Issuance of debt, principal amount										$ 350,000,000
Stated interest rate (as a percent)										3.25%
Subsequent Event [Member] \| Senior Notes [Member] \| Southern Gas Company Capital [Member]
Debt Instrument [Line Items]
Stated interest rate (as a percent)	6.375%
Repayments of senior notes	$ 300,000,000
First Mortgage Bonds [Member] \| Secured Debt [Member] \| Nicor Gas [Member]
Debt Instrument [Line Items]
Repayments of first mortgage bond		$ 50,000,000		$ 75,000,000
Issuance of debt, principal amount								$ 250,000,000
First Mortgage Bonds Due 2026 [Member] \| Secured Debt [Member] \| Nicor Gas [Member]
Debt Instrument [Line Items]
Issuance of debt, principal amount								$ 100,000,000
Stated interest rate (as a percent)								2.66%
First Mortgage Bonds Due 2031 [Member] \| Secured Debt [Member] \| Nicor Gas [Member]
Debt Instrument [Line Items]
Issuance of debt, principal amount								$ 100,000,000
Stated interest rate (as a percent)								2.91%
First Mortgage Bonds Due 2036 [Member] \| Secured Debt [Member] \| Nicor Gas [Member]
Debt Instrument [Line Items]
Issuance of debt, principal amount								$ 50,000,000
Stated interest rate (as a percent)								3.27%
Cash Flow Hedging [Member] \| Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Notional amount					$ 800,000,000	$ 200,000,000
Derivatives settled during period, notional amount									$ 400,000,000			$ 200,000,000
Loss on settlement of derivative			$ 26,000,000
Cash Flow Hedging [Member] \| Minimum [Member] \| Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Derivative term					10 years
Cash Flow Hedging [Member] \| Maximum [Member] \| Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Derivative term					30 years