Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable, after Allowance for Credit Loss, Current [Abstract]
Accounts receivable, net	$ 119,877	$ 94,791
Contract with Customer, Asset, after Allowance for Credit Loss, Current [Abstract]
Contract assets	15,300	14,800
Contract with Customer, Liability [Abstract]
Current contract liabilities	25,724	25,776
Contract liabilities	25,700	$ 25,800
Revenue recognized	$ 24,600