FAIR VALUE MEASUREMENT OF FINANCIAL INSTRUMENTS - Schedule of Assets Measured at Fair Value (Details) - Recurring Fair Value Measurements - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022
Assets
Short-term investments:	$ 85,090	$ 117,101
Non-qualified supplemental savings plan	14,578	14,301
Debt security investment in Galileo	33,000	33,000
Other debt securities	2,140	565
Total investments	235,659	195,236
Liabilities
Contingent consideration	5,030	4,022
ADNOC Drilling
Assets
Equity investment	171,745	147,370
Tamboran Resources Limited
Assets
Equity investment	14,196
Level 1
Assets
Short-term investments:	13,106	18,837
Non-qualified supplemental savings plan	14,578	14,301
Debt security investment in Galileo	0
Other debt securities	0	0
Total investments	200,519	161,671
Liabilities
Contingent consideration	0	0
Level 1 \| ADNOC Drilling
Assets
Equity investment	171,745	147,370
Debt security investment in Galileo		0
Level 1 \| Tamboran Resources Limited
Assets
Equity investment	14,196
Level 2
Assets
Short-term investments:	71,984	98,264
Non-qualified supplemental savings plan	0	0
Debt security investment in Galileo	0	0
Other debt securities	0	0
Total investments	0	0
Liabilities
Contingent consideration	0	0
Level 2 \| ADNOC Drilling
Assets
Equity investment	0	0
Level 2 \| Tamboran Resources Limited
Assets
Equity investment	0
Level 3
Assets
Short-term investments:	0	0
Non-qualified supplemental savings plan	0	0
Equity investment		0
Debt security investment in Galileo	33,000	33,000
Other debt securities	2,140	565
Total investments	35,140	33,565
Liabilities
Contingent consideration	5,030	4,022
Level 3 \| ADNOC Drilling
Assets
Equity investment	0
Level 3 \| Tamboran Resources Limited
Assets
Equity investment	0
Corporate debt securities
Assets
Short-term investments:	71,984	98,264
Corporate debt securities \| Level 1
Assets
Short-term investments:	0	0
Corporate debt securities \| Level 2
Assets
Short-term investments:	71,984	98,264
Corporate debt securities \| Level 3
Assets
Short-term investments:	0	0
U.S. government and federal agency securities
Assets
Short-term investments:	13,106	18,837
U.S. government and federal agency securities \| Level 1
Assets
Short-term investments:	13,106	18,837
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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