Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Exchangeable notes, fair value	$ 102,064
Accrued Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	18,226	$ 5,999
Contingent consideration accrued at time of business combination	4,748	13,032
Change in fair value of contingent consideration included in Operating expenses	(1,409)	3,389
Contingent consideration paid	(8,531)	(4,194)
Balance, ending	13,034	18,226
Accrued Expenses and Other Current Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	10,062	10,223
Other Long-term Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	$ 2,972	$ 8,003