Contract Balance - Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Billed	$ 164,659	$ 198,305
Unbilled	156,018	155,408
Receivables Gross	320,677	353,713
Less: allowance for doubtful accounts	(3,780)	(4,154)
Accounts Receivable, after Allowance for Credit Loss	316,897	349,559
Less: long-term receivables	(43,541)	(37,452)
Accounts receivable, net	$ 273,356	$ 312,107

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 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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