Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
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	0	4,000
Change in the fair value of warrant liabilities, included in Other expenses	154	(349)
Contingent consideration paid	0	(1,600)
Balance, ending	18,380	$ 8,050
Accrued Expenses and Other Current Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	12,134		$ 10,223
Other Long-term Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	$ 6,246		$ 8,003