Revenue from Contracts with Customers - Contract Balances - Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Billed Receivables	$ 203,351	$ 198,305
Unbilled Receivables	165,386	155,408
Receivables Gross	368,737	353,713
Allowance for doubtful accounts	(4,218)	(4,154)	$ (5,072)
Net receivables	364,519	349,559
Accounts Receivable, net , noncurrent	(42,109)	(37,452)
Accounts receivable, net	322,410	312,107
Expense, Allowance for Credit Loss	2,300	652
Write-off	$ (2,236)	$ (1,570)