Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Exchangeable notes, fair value	$ 119,633
Accrued Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	13,034	$ 18,226
Contingent consideration accrued at time of business combination	22,577	4,748
Change in fair value of contingent consideration included in Operating expenses	7,140	(1,409)
Contingent consideration paid	(6,522)	(8,531)
Balance, ending	36,229	13,034
Accrued Expenses and Other Current Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	25,768	10,062
Other Long-term Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	$ 10,461	$ 2,972