Debt Instrument, Remaining Maturity Term

No definition available.

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- 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

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 835

-SubTopic 30

-Section 45

-Paragraph 2

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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+ Details

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: 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

+ Details

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Period Type:	instant

- 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 carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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-Name Accounting Standards Codification

-Topic 944

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-Section S99

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-Subparagraph (SX 210.7-03.16)

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20, 22

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+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ 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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (b)

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).

+ References

+ Details

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Period Type:	duration

- Definition

The net cash inflow or cash outflow from issuing (borrowing) and repaying commercial paper.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 9

-Subparagraph c

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+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from a borrowing having initial term of repayment of more than three months but less than one year or one operating cycle (if the normal cycle is more than one year).

+ References

+ Details

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Period Type:	duration

- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

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- Definition

The cash outflow due to repaying amounts borrowed by issuing commercial paper.

+ 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)

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-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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Period Type:	duration

- Definition

The cash outflow from a repayment of a borrowing having initial term of repayment of more than three months but less than one year or one operating cycle (if the normal cycle is more than one year).

+ References

+ Details

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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Note 8 - Debt and Credit Facilities (Details) (USD $)	12 Months Ended
Note 8 - Debt and Credit Facilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 23, 2015
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Proceeds from (Repayments of) Commercial Paper	$ 4,000,000	$ (206,000,000)	$ 56,000,000
Repayments of Commercial Paper	225,000,000us-gaap_RepaymentsOfCommercialPaper
Proceeds from Issuance of Senior Long-term Debt	0	494,000,000
Long-term Debt	3,706,000,000us-gaap_LongTermDebt
Convert to Variable Rate [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Senior Notes	120,000,000
Debt Instrument, Interest Rate, Stated Percentage	1.90%
Refinanced [Member] \| Refunding Bonds [Member] \| Gas Facility Revenue Bonds [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Long-term Debt		60,000,000
Refinanced [Member] \| Purchase of Existing Bonds [Member] \| Gas Facility Revenue Bonds [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Long-term Debt		140,000,000
Refinanced [Member] \| Gas Facility Revenue Bonds [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Long-term Debt		200,000,000
Commercial Paper [Member] \| Minimum [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Debt Instrument, Term	1 day
Debt Instrument, Remaining Maturity Term		2 days
Commercial Paper [Member] \| Maximum [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Debt Instrument, Term	108 days
Debt Instrument, Remaining Maturity Term	70 days
Commercial Paper [Member] \| AGL Capital [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	0.50%
Commercial Paper [Member] \| Nicor Gas [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	0.40%
Commercial Paper [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Proceeds from Short-term Debt, Maturing in More than Three Months	50,000,000
Repayments of Short-term Debt, Maturing in More than Three Months	195,000,000
Target ratio [Member] \| Minimum [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Ratio of Indebtedness to Net Capital	0.50
Target ratio [Member] \| Maximum [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Ratio of Indebtedness to Net Capital	0.60
Senior Notes [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Debt Instrument, Term		30 years
Debt Instrument, Interest Rate, Stated Percentage		4.40%
Proceeds from Issuance of Long-term Debt		500,000,000
Long-term Debt	2,625,000,000	2,825,000,000
Gas Facility Revenue Bonds [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Long-term Debt	200,000,000	200,000,000
Interest Rate Swap [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Derivative, Notional Amount				800,000,000
AGL Capital [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Long-term Line of Credit	0	0
Nicor Gas [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Long-term Line of Credit	$ 0	$ 0
Maximum [Member]
Note 8 - Debt and Credit Facilities (Details) [Line Items]
Ratio of Indebtedness to Net Capital	0.70