Assets Acquired [Abstract]

No definition available.

Name:	ffiv_AssetsAcquiredAbstractAbstract
Namespace Prefix:	ffiv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Business Combination, Recognized Identifiable Asset Acquired and Liability Assumed, Operating Lease, Lease Liabilities

+ References

No definition available.

+ Details

Name:	ffiv_BusinessCombinationRecognizedIdentifiableAssetAcquiredandLiabilityAssumedOperatingLeaseLeaseLiabilities
Namespace Prefix:	ffiv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Business Combination, Recognized Identifiable Asset Acquired and Liability Assumed, Operating Lease, Right-Of-Use Assets

+ References

No definition available.

+ Details

Name:	ffiv_BusinessCombinationRecognizedIdentifiableAssetAcquiredandLiabilityAssumedOperatingLeaseRightOfUseAssets
Namespace Prefix:	ffiv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair Value of intangible Assets [Abstract]

+ References

No definition available.

+ Details

Name:	ffiv_FairValueOfIntangibleAssetsAbstractAbstract
Namespace Prefix:	ffiv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Liabilities Assumed [Abstract]

+ References

No definition available.

+ Details

Name:	ffiv_LiabilitiesAssumedAbstractAbstract
Namespace Prefix:	ffiv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-URI https://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275

+ Details

Name:	us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of assets acquired at the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=128092470&loc=d3e4845-128472

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer, acquired at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of other assets expected to be realized or consumed before one year or the normal operating cycle, if longer, acquired at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of deferred revenue expected to be recognized as such within one year or the normal operating cycle, if longer, assumed at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesDeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred tax asset attributable to deductible temporary differences and carryforwards acquired at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of identifiable intangible assets recognized as of the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 55
-Paragraph 37
-URI https://asc.fasb.org/extlink&oid=123455525&loc=d3e2207-128464

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=128092470&loc=d3e4845-128472

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of liabilities assumed at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 55
-Paragraph 24
-URI https://asc.fasb.org/extlink&oid=122137925&loc=d3e14258-109268

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(15))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ffiv_ThreatStackIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_DevelopedTechnologyRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ffiv_VolterraIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ffiv_ShapeSecurityInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TradeNamesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Business Combinations - Purchase Price Allocation (Details) - USD ($)	Oct. 01, 2021	Jan. 22, 2021	Jan. 24, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Fair Value of intangible Assets Abstract [Abstract]
Goodwill				$ 2,259,282,000	$ 2,216,553,000	$ 1,858,966,000
Threat Stack, Inc.
AssetsAcquiredAbstract [Abstract]
Cash, cash equivalents, and restricted cash	$ 911,000
Fair Value of intangible Assets Abstract [Abstract]
Deferred tax assets	14,036,000
Other tangible assets acquired, at fair value	$ 5,481,000
Identifiable Intangible Assets Useful Life	5 years
Goodwill	$ 43,287,000
Total assets acquired	79,515,000
Liabilities assumed
Deferred revenue	(10,591,000)
Total liabilities assumed	(10,591,000)
Net assets acquired	68,924,000
Threat Stack, Inc. \| Developed Technology Rights
Fair Value of intangible Assets Abstract [Abstract]
Identifiable intangible assets:	$ 11,400,000
Identifiable Intangible Assets Useful Life	5 years
Threat Stack, Inc. \| Customer Relationships
Fair Value of intangible Assets Abstract [Abstract]
Identifiable intangible assets:	$ 4,400,000
Identifiable Intangible Assets Useful Life	5 years
Volterra, Inc.
AssetsAcquiredAbstract [Abstract]
Cash, cash equivalents, and restricted cash		$ 14,012,000
Fair Value of intangible Assets Abstract [Abstract]
Other tangible assets acquired, at fair value		$ 7,499,000
Identifiable Intangible Assets Useful Life		6 years 11 months 12 days
Goodwill		$ 350,863,000
Total assets acquired		432,374,000
Liabilities assumed
Total liabilities assumed		(5,233,000)
Net assets acquired		427,141,000
Volterra, Inc. \| Developed Technology Rights
Fair Value of intangible Assets Abstract [Abstract]
Identifiable intangible assets:		$ 59,500,000
Identifiable Intangible Assets Useful Life		7 years
Volterra, Inc. \| Customer Relationships
Fair Value of intangible Assets Abstract [Abstract]
Identifiable intangible assets:		$ 500,000
Identifiable Intangible Assets Useful Life		1 year
Shape Security, Inc.
AssetsAcquiredAbstract [Abstract]
Cash, cash equivalents, and restricted cash			$ 53,934,000
Fair Value of intangible Assets Abstract [Abstract]
Accounts receivable			21,077,000
Deferred tax assets			29,848,000
Operating lease right-of-use assets			29,644,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other			$ 22,571,000
Identifiable Intangible Assets Useful Life			6 years 6 months
Goodwill			$ 798,867,000
Total assets acquired			1,106,441,000
Liabilities assumed
Deferred revenue			(39,000,000)
Operating lease liabilities			(30,773,000)
Other assumed liabilities			(18,571,000)
Total liabilities assumed			(88,344,000)
Net assets acquired			1,018,097,000
Shape Security, Inc. \| Developed Technology Rights
Fair Value of intangible Assets Abstract [Abstract]
Identifiable intangible assets:			$ 120,000,000
Identifiable Intangible Assets Useful Life			7 years
Shape Security, Inc. \| Customer Relationships
Fair Value of intangible Assets Abstract [Abstract]
Identifiable intangible assets:			$ 21,000,000
Identifiable Intangible Assets Useful Life			4 years
Shape Security, Inc. \| Trade Names
Fair Value of intangible Assets Abstract [Abstract]
Identifiable intangible assets:			$ 9,500,000
Identifiable Intangible Assets Useful Life			5 years