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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - SOFTWARE COSTS (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024 | Sep. 30, 2024
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Capitalized software costs | $ 10,784 |  | $ 10,784 |  | $ 10,522
Operation and maintenance |  |  |  |  |
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Software costs | 1,335 | $ 4,048 | 5,221 | $ 9,975 |
Depreciation and amortization |  |  |  |  |
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Software costs | 3,190 | $ 1,507 | 8,733 | $ 3,761 |
Utility plant, at cost |  |  |  |  |
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Software costs | 133,498 |  | 133,498 |  | 133,158
Construction work in progress | Regulated |  |  |  |  |
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Software costs | 64,854 |  | 64,854 |  | 26,659
Nonutility plant and equipment, at cost |  |  |  |  |
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Software costs | 344 |  | 344 |  | 344
Accumulated depreciation and amortization, utility plant |  |  |  |  |
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Accumulated depreciation and amortization | (22,357) |  | (22,357) |  | (13,632)
Accumulated depreciation and amortization, nonutility plant and equipment |  |  |  |  |
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items] |  |  |  |  |
Accumulated depreciation and amortization | $ (56) |  | $ (56) |  | $ (48)

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- Definition Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 985 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481283/985-20-50-2 + Details
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