| **FAIR VALUE MEASUREMENTS (Policies)** | 6 Months Ended                                                                                                                 |
|----------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|
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| **FAIR VALUE MEASUREMENTS [Abstract]** | Â                                                                                                                              |
| Transfer Policy                        | Transfers into and out of Level 3 are determined using values at the end of the interim period in which the transfer occurred. |

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| - Definition
FAIR VALUE MEASUREMENTS
+ Details**Name:**gas_FairValueMeasurementsAbstract**Namespace Prefix:**gas**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure of accounting policy for determining when transfers between levels are recognized.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258
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