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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ADDITIONAL INFORMATION (Details) - USD ($) |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 8 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
May 26, 2021 | Dec. 31, 2019 | Jun. 30, 2021 | Jun. 30, 2020 | Mar. 31, 2021 | May 26, 2021 | Jun. 30, 2021 | Jun. 30, 2020 | Sep. 30, 2020
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |
Payment to acquire building | $ 41,100,000 |  |  |  |  |  |  |  |
Reserve for expected credit losses |  |  |  |  |  |  | $ 15,288,000 | $ 1,657,000 |
Loans receivable in other current assets |  |  | $ 14,300,000 |  |  |  | 14,300,000 |  | $ 13,700,000
Loans receivable in other noncurrent assets |  |  | 33,200,000 |  |  |  | 33,200,000 |  | $ 35,300,000
Proceeds from sale leaseback transaction |  |  |  |  |  |  | 0 | 4,000,000 |
Proceeds from sale leaseback transaction - solar |  |  | $ 5,500,000 | $ 42,900,000 |  |  | 17,673,000 | $ 42,927,000 |
Clean Energy Ventures |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |
Reserve for expected credit losses |  |  |  |  | $ 5,200,000 |  |  |  |
Natural Gas Distribution |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |
Sale leaseback transaction, lease term |  |  |  |  |  | 16 years |  |  |
Proceeds from sale leaseback transaction |  | $ 4,000,000.0 |  |  |  |  | $ 0 |  |
Minimum |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |
Loans receivable, term |  |  |  |  |  |  | 2 years |  |
Maximum |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |
Loans receivable, term |  |  |  |  |  |  | 10 years |  |

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