FAIR VALUE MEASUREMENTS - Changes in Level 3 Financial Instruments Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2021
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Exchangeable notes, fair value	$ 107,453
Accrued Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	36,229	$ 13,034
Contingent consideration accrued at time of business combination	6,281	22,403
Change in fair value of contingent consideration included in Operating expenses	24,684	5,835
Contingent consideration paid	(28,783)	(6,522)
Balance, ending	38,411	$ 34,750
Accrued Expenses and Other Current Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	27,327		$ 25,768
Other Long-term Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	$ 11,084		$ 10,461