Revenue from Contracts with Customers - Contract Balances - Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Billed Receivables	$ 234,745	$ 203,351
Unbilled Receivables	203,896	165,386
Receivables Gross	438,641	368,737
Allowance for doubtful accounts	(4,978)	(4,218)	$ (4,154)
Net receivables	433,663	364,519
Accounts Receivable, net , noncurrent	(45,716)	(42,109)
Accounts receivable, net	387,947	322,410
Expense, Allowance for Credit Loss	1,475	2,300
Write-off	$ (715)	$ (2,236)

Receivables, Gross

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Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

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Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

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Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as noncurrent.

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Amount of direct write-downs of accounts receivable charged against the allowance.

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Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer.

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