Revenue from Contracts with Customers - Contract Balances - Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Billed	$ 327,721	$ 264,942
Unbilled	246,600	210,795
Accounts receivable, gross	574,321	475,737
Less: allowance for doubtful accounts	(7,964)	(6,454)	$ (4,978)
Net receivables	566,357	469,283
Less: long-term receivables	(37,209)	(42,641)
Accounts receivable, net	$ 529,148	$ 426,642

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 of allowance for credit loss on accounts receivable.

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Amounts due for billed services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the Company and, at a minimum, one other party. An example would be amounts billed to customers under contracts or programs but not paid as of the balance sheet date.

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Unbilled amounts due for services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the entity and, at a minimum, one other party. An example would be amounts associated with contracts or programs where the recognized revenue for performance thereunder exceeds the amounts billed under the terms thereof as of the date of the balance sheet.

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