Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Mezzanine Warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	$ 0	$ 767
Change in the fair value of warrant liabilities, included in Other expenses		8,487
Settlement through exercise of warrants or payment of consideration		(9,254)
Balance, ending	0	0
Accrued Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	5,999	3,340
Change in the fair value of warrant liabilities, included in Other expenses	3,389	3,851
Contingent consideration accrued at time of business combination	13,032	1,877
Settlement through exercise of warrants or payment of consideration	(4,194)	(3,069)
Balance, ending	$ 18,226	5,999
Accrued Expenses and Other Current Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration		10,223	$ 3,813
Other Long-term Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration		$ 8,003	$ 2,186