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v3.25.3

Segment Information - Narrative (Details) - geographic_region | 12 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Segment Reporting Information [Line Items] |  |  |
Number of Geographic Regions | 3 | 3 | 3

X
- Definition Number of Geographic Regions + References No definition available. + Details
Name: | ffiv_NumberofGeographicRegions
Namespace Prefix: | ffiv_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition 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. + References No definition available. + Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration