v3.26.1
FAIR VALUE MEASUREMENT OF FINANCIAL INSTRUMENTS (Tables)
 9 Months Ended
Jun. 30, 2026
Fair Value Disclosures [Abstract]  
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis
The following tables summarize our financial assets and liabilities measured at fair value on a recurring basis and indicate the level in the fair value hierarchy in which we classify the fair value measurement as of the dates indicated below:
June 30, 2026
(in thousands)Fair Value    Level 1    Level 2    Level 3
Assets
Short-term investments:
Money market mutual funds$5,040 $5,040 $— $— 
Corporate debt securities21,920 — 21,920 — 
Total26,960 5,040 21,920 — 
Long-term Investments:
Recurring fair value measurements:
Equity securities:
Non-qualified supplemental savings plan19,196 19,196 — — 
Investment in Tamboran32,663 32,663 — — 
Debt securities:
Geothermal debt securities, net2,000 — — 2,000 
Other debt securities250 — — 250 
Total$54,109 $51,859 $— $2,250 
September 30, 2025
(in thousands)Fair Value    Level 1    Level 2    Level 3
Assets
Short-term investments:
Corporate debt securities$21,302 $— $21,302 $— 
Total21,302 — 21,302 — 
Long-term investments:
Recurring fair value measurements:
Equity securities:
Non-qualified supplemental savings plan17,662 17,662 — — 
Investment in Tamboran25,976 25,976 — — 
Other equity securities1,449 1,449 — — 
Debt securities:
Geothermal debt securities, net2,000 — — 2,000 
Other debt securities250 — — 250 
Total$47,337 $45,087 $— $2,250 
Schedule of Reconciliation of Long Term Debt Securities Available For Sale, Classified as Level 3
The following table reconciles changes in the balance of our equity securities, without readily determinable fair values, including investments that have been marked to fair value on a nonrecurring basis, for the periods presented below:
Three Months Ended June 30,Nine Months Ended June 30,
(in thousands)2026202520262025
Assets at beginning of period$17,547 $45,519 $20,861 $30,090 
Purchases1,201 594 2,239 1,528 
Disposals— (27,117)— (27,117)
Sales
— — (124)— 
Transfer in— 320 — 320 
Total gain (loss):
Included in earnings— 624 (4,228)15,119 
Assets at end of period$18,748 $19,940 $18,748 $19,940 
Schedule of Supplemental Fair Value Information about Long-Term Fixed-Rate Debt
The following information presents the supplemental fair value information for our long-term fixed-rate debt, net at June 30, 2026 and September 30, 2025:
Carrying Value at June 30, 2026
Fair Value at June 30, 2026
Using Inputs Considered as:
(in thousands)
Level 1
Level 2
    
Level 3
Unsecured senior notes:
2027 Notes$348,446 $— $349,793 $— 
2029 Notes347,158 — 350,315 — 
2031 Notes546,787 — 494,197 — 
2034 Notes543,629 — 539,391 — 
Secured term loan credit agreements:
2023 Oman Facility
32,970 — — 32,970 
2024 Oman Facility
36,267 — — 36,267 
Total long-term debt, net of current portion
$1,855,257 $— $1,733,696 $69,237 
Carrying Value at September 30, 2025
Fair Value at September 30, 2025
Using Inputs Considered as:
(in thousands)Level 1Level 2    Level 3
Unsecured senior notes:
2027 Notes$347,675 $— $352,261 $— 
2029 Notes346,602 — 348,688 — 
2031 Notes546,336 — 486,343 — 
2034 Notes543,197 — 538,417 — 
Unsecured term loan credit agreement:
2027 Term Loan199,020 — 201,292 — 
Secured term loan credit agreements:
2023 Oman Facility35,465 — — 35,465 
2024 Oman Facility38,789 — — 38,789 
Total long-term debt, net of current portion$2,057,084 $— $1,927,001 $74,254