Commitments and Contingencies - Schedule of Future Minimum Lease Payments for Hosting, Telecommunication Usage Services (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Hosting Services
Unrecorded Unconditional Purchase Obligation [Line Items]
2024	$ 246
2025	4
2026	0
2027	0
Thereafter	0
Total future minimum payment	250
Telecommunication Usage Services
Unrecorded Unconditional Purchase Obligation [Line Items]
2024	7,619
2025	3,144
2026	1,871
2027	1,358
Thereafter	685
Total future minimum payment	$ 14,677

Purchase Obligation, Due after the Fourth Year

No definition available.

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Namespace Prefix:	fivn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

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

- Definition

Amount of purchase arrangement to be paid in fourth fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

+ Details

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

- Definition

Amount of purchase arrangement to be paid in next fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

+ Details

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

- Definition

Amount of purchase arrangement to be paid in second fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

+ Details

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

- Definition

Amount of purchase arrangement to be paid in third fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

+ Details

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

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 440
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482648/440-10-50-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 440
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482648/440-10-50-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 440
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482648/440-10-50-4

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=fivn_TelecommunicationUsageServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: