FAIR VALUE MEASUREMENT OF FINANCIAL INSTRUMENTS - Schedule of Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Assets
Short-term investments:	$ 84,121	$ 93,600
Total	237,643	239,145
Other equity securities	2,721
Recurring Fair Value Measurements
Assets
Non-qualified supplemental savings plan	16,478	14,597
Investment in Galileo	35,868	35,434
Geothermal debt securities	2,000	2,006
Total	234,922	236,715
Liabilities
Contingent consideration	8,350	9,455
Recurring Fair Value Measurements \| ADNOC Drilling
Assets
Equity investment	164,339	174,758
Recurring Fair Value Measurements \| Tamboran Resources Limited
Assets
Equity investment	16,237	9,920
Fair Value, Nonrecurring
Assets
Other equity securities		2,430
Liabilities
Equity securities	25,200	25,200
Fair Value, Nonrecurring \| Geothermal Investments
Assets
Equity investment	3,300	3,000
Other equity securities		2,430
Liabilities
Equity securities	600	600
Other equity securities	2,700	2,400
Level 1
Assets
Short-term investments:	46,278	44,836
Total	197,054	199,275
Other equity securities	0
Level 1 \| Recurring Fair Value Measurements
Assets
Non-qualified supplemental savings plan	16,478	14,597
Investment in Galileo	0	0
Geothermal debt securities	0	0
Total	197,054	199,275
Liabilities
Contingent consideration	0	0
Level 1 \| Recurring Fair Value Measurements \| ADNOC Drilling
Assets
Equity investment	164,339	174,758
Level 1 \| Recurring Fair Value Measurements \| Tamboran Resources Limited
Assets
Equity investment	16,237	9,920
Level 1 \| Fair Value, Nonrecurring
Assets
Other equity securities		0
Level 1 \| Fair Value, Nonrecurring \| Geothermal Investments
Assets
Other equity securities		0
Level 2
Assets
Short-term investments:	37,843	48,764
Total	0	0
Other equity securities	0
Level 2 \| Recurring Fair Value Measurements
Assets
Non-qualified supplemental savings plan	0	0
Investment in Galileo	0	0
Geothermal debt securities	0	0
Total	0	0
Liabilities
Contingent consideration	0	0
Level 2 \| Recurring Fair Value Measurements \| ADNOC Drilling
Assets
Equity investment	0	0
Level 2 \| Recurring Fair Value Measurements \| Tamboran Resources Limited
Assets
Equity investment	0	0
Level 2 \| Fair Value, Nonrecurring
Assets
Other equity securities		0
Level 2 \| Fair Value, Nonrecurring \| Geothermal Investments
Assets
Other equity securities		0
Level 3
Assets
Short-term investments:	0	0
Total	40,589	39,870
Other equity securities	2,721
Level 3 \| Recurring Fair Value Measurements
Assets
Non-qualified supplemental savings plan	0	0
Investment in Galileo	35,868	35,434
Geothermal debt securities	2,000	2,006
Total	37,868	37,440
Liabilities
Contingent consideration	8,350	9,455
Level 3 \| Recurring Fair Value Measurements \| ADNOC Drilling
Assets
Equity investment	0	0
Level 3 \| Recurring Fair Value Measurements \| Tamboran Resources Limited
Assets
Equity investment	0	0
Level 3 \| Fair Value, Nonrecurring
Assets
Other equity securities		2,430
Level 3 \| Fair Value, Nonrecurring \| Geothermal Investments
Assets
Other equity securities		2,430
Corporate and municipal debt securities
Assets
Short-term investments:	37,843	48,764
Corporate and municipal debt securities \| Level 1
Assets
Short-term investments:	0	0
Corporate and municipal debt securities \| Level 2
Assets
Short-term investments:	37,843	48,764
Corporate and municipal debt securities \| Level 3
Assets
Short-term investments:	0	0
U.S. government and federal agency securities
Assets
Short-term investments:	46,278	44,836
U.S. government and federal agency securities \| Level 1
Assets
Short-term investments:	46,278	44,836
U.S. government and federal agency securities \| Level 2
Assets
Short-term investments:	0	0
U.S. government and federal agency securities \| Level 3
Assets
Short-term investments:	$ 0	$ 0

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