Contract Balances and Performance Obligation - Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Accounts Receivable, after Allowance for Credit Loss, Noncurrent	$ (32,773)	$ (34,370)
Accounts receivable, net	307,307	297,427
Accounts Receivable, before Allowance for Credit Loss	199,102	206,714
Unbilled Receivables, Current	146,226	127,651
Receivables Gross	345,328	334,365
Accounts Receivable, Allowance for Credit Loss	(5,248)	(2,568)
Accounts Receivable, after Allowance for Credit Loss	$ 340,080	$ 331,797

Receivables, Gross

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- Definition

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 allowance for credit loss on accounts receivable.

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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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