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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill (Details) $ in Millions | 3 Months Ended
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Dec. 31, 2016 USD ($)
Goodwill [Roll Forward] |
Balance as of September 30, 2016 | $ 1,164.9
Adjustments related to the acquisition of EnergySouth | (3.5)
Balance as of December 31, 2016 | 1,161.4
Operating Segments | Gas Utility |
Goodwill [Roll Forward] |
Balance as of September 30, 2016 | 210.2
Adjustments related to the acquisition of EnergySouth | 0.0
Balance as of December 31, 2016 | 210.2
Operating Segments | Gas Marketing |
Goodwill [Roll Forward] |
Balance as of September 30, 2016 | 0.0
Adjustments related to the acquisition of EnergySouth | 0.0
Balance as of December 31, 2016 | 0.0
Other |
Goodwill [Roll Forward] |
Balance as of September 30, 2016 | 954.7
Adjustments related to the acquisition of EnergySouth | (3.5)
Balance as of December 31, 2016 | $ 951.2

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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975 + Details
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- Definition Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e961-128460 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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