Contract Balance - Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Billed	$ 138,608	$ 198,305
Unbilled	156,132	155,408
Receivables Gross	294,740	353,713
Less: allowance for doubtful accounts	(4,282)	(4,154)
Accounts Receivable, after Allowance for Credit Loss	290,458	349,559
Less: long-term receivables	(30,297)	(37,452)
Accounts receivable, net	$ 260,161	$ 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 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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