REPORTING SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 3,960,740	$ 3,928,507
Assets held for sale	224,898	0
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	3,973,559	3,922,001
Operating Segments \| Natural Gas Distribution
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,567,347	2,519,578
Operating Segments \| Clean Energy Ventures
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	812,789	771,340
Operating Segments \| Energy Services
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	366,322	398,277
Operating Segments \| Midstream
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	227,101	232,806
Home Services and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	107,415	114,801
Intercompany Assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ (120,234)	$ (108,295)

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: 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(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Amount of assets held-for-sale that are not part of a disposal group, expected to be sold within a year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 15
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=77912953&loc=d3e400-110220

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