SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RELATED RISKS AND UNCERTAINTIES - Narrative (Details) shares in Millions	1 Months Ended	3 Months Ended			9 Months Ended
	Oct. 31, 2022 USD ($) shares	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2023 USD ($) geographical_area	Jun. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents		$ 61,400,000	$ 33,900,000		$ 61,400,000	$ 33,900,000	$ 36,900,000	$ 19,200,000
Additional cash and cash equivalents restricted at the election of management for potential insurance claims		60,700,000			60,700,000		35,800,000
Receivables		449,588,000			449,588,000		458,713,000
Contract liability		34,726,000			34,726,000		20,646,000
Operating revenues		723,956,000	550,233,000		2,212,815,000	1,427,612,000
Underwriting expense		5,500,000	3,100,000		10,200,000	2,700,000
Casualty insurance premiums		9,700,000	9,400,000		30,600,000	26,200,000
Premium revenues and expenses		17,400,000	14,700,000		51,400,000	41,600,000
Stop-loss program, maximum amount of claim				$ 50,000
Stop-loss medical expenses		2,100,000	3,800,000		$ 7,400,000	10,600,000
Cumulative inflation rate before a country is considered highly inflationary					100.00%
Foreign currency losses		1,400,000	1,200,000		$ 1,700,000	4,500,000
Tamboran Resources Limited
Summary Of Significant Accounting Policies [Line Items]
Payments to acquire investments	$ 14,100,000
Investment shares acquired (in shares) | shares	106.0
Investee
Summary Of Significant Accounting Policies [Line Items]
Receivables		6,700,000			6,700,000
Contract liability		5,700,000			5,700,000
Expected revenue		35,200,000
International Solutions
Summary Of Significant Accounting Policies [Line Items]
Operating revenues		$ 48,692,000	$ 29,118,000		$ 159,383,000	$ 93,699,000
International Locations | Geographic Concentration Risk | Operating Revenue
Summary Of Significant Accounting Policies [Line Items]
Concentration percentage		6.80%	5.40%		7.30%	6.70%
Minimum
Summary Of Significant Accounting Policies [Line Items]
Number of geographical areas operating | geographical_area					1
Argentina
Summary Of Significant Accounting Policies [Line Items]
Operating revenues		$ 32,388,000	$ 18,615,000		$ 101,712,000	$ 63,216,000
Cash		$ 24,000,000			$ 24,000,000
South America | International Locations | Geographic Concentration Risk | Operating Revenue | International Solutions
Summary Of Significant Accounting Policies [Line Items]
Concentration percentage		84.80%	82.60%		87.30%	78.40%
Acquisition of Drilling Technologies Companies
Summary Of Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents		$ 700,000			$ 700,000		$ 1,100,000