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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - RECEIVABLE BY SUBSIDIARY (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Establishment of allowance for doubtful accounts, customer account balances, days outstanding (more than) |  | 60 days |
Billed |  | $ 205,490 | $ 196,467
Receivable by subsidiary percentage |  | 100.00% | 100.00%
Unbilled revenues |  | $ 7,199 | $ 7,202
Energy Services |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Billed |  | $ 157,936 | $ 150,322
Receivable by subsidiary percentage |  | 77.00% | 77.00%
Natural Gas Distribution |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Billed | [1] | $ 39,151 | $ 37,432
Receivable by subsidiary percentage | [1] | 19.00% | 19.00%
Clean Energy Ventures |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Billed |  | $ 3,330 | $ 2,655
Receivable by subsidiary percentage |  | 2.00% | 1.00%
Home Services and Other Operations |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Billed |  | $ 5,073 | $ 6,058
Receivable by subsidiary percentage |  | 2.00% | 3.00%
[1] | Does not include unbilled revenues of $7.2 million as of September 30, 2018 and 2017.

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