Stock option plan - Reserved For Issuance (Detail) - 2018 ESPP [Member] shares in Thousands	12 Months Ended
Sep. 30, 2021 shares
Disclosure Of Employee Stock Purchase Plan [Line Items]
Outstanding at September 30, 2020	179
Additional shares authorized	250
Shares issued during the period	(74)
Outstanding at September 30, 2021	355

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Aggregate number of common shares reserved for future issuance.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
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- Definition

Number of additional shares authorized for issuance under share-based payment arrangement.

+ References

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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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