Accounts Receivable (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2021	Sep. 30, 2020
Receivables [Abstract]
Accounts receivable	$ 231,227	$ 264,536
Allowance for credit losses	(3,884)	(4,057)
Accounts receivable, net	227,343	$ 260,479
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at September 30, 2020	(4,057)
Charged to costs and expenses	(12)
Write-offs	209
Foreign currency and other	(24)
Balance at December 31, 2020	$ (3,884)