<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2019-01-31"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="fivn-20200803.xsd" xlink:type="simple"/>
    <context id="i1b60c243691642fbb20e1511af116955_D20200803-20200803">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001288847</identifier>
        </entity>
        <period>
            <startDate>2020-08-03</startDate>
            <endDate>2020-08-03</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF80L2ZyYWc6ZjRmNzRjYTc0NzE5NDlmYzkyMzQ4Y2Y4ZDMyODI3NmYvdGFibGU6ODc0Njk1NmRiZmVkNGM3NzhjNDhiYjM1MmJlZjA0NWYvdGFibGVyYW5nZTo4NzQ2OTU2ZGJmZWQ0Yzc3OGM0OGJiMzUyYmVmMDQ1Zl8yLTEtMS0xLTA_69b2ae5a-35a5-41a9-9dcf-88f9b4cc54d4">0001288847</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF80L2ZyYWc6ZjRmNzRjYTc0NzE5NDlmYzkyMzQ4Y2Y4ZDMyODI3NmYvdGFibGU6ODc0Njk1NmRiZmVkNGM3NzhjNDhiYjM1MmJlZjA0NWYvdGFibGVyYW5nZTo4NzQ2OTU2ZGJmZWQ0Yzc3OGM0OGJiMzUyYmVmMDQ1Zl81LTEtMS0xLTA_713267a5-e105-4578-9a09-1db6c65fba35">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV84Mg_fdf9ab13-e52e-47a2-a582-5f05f0f5b0db">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8yMjM_f086234a-3ece-4a6c-9485-795132352c03">2020-08-03</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8yMjY_590c6e6c-90ca-4c1e-bea4-09fecd66efdc">FIVE9, INC.</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6ODEyYjM0NzkwNzRjNDAxYmI0MGQzNWE4ZGFjYTliZDAvdGFibGVyYW5nZTo4MTJiMzQ3OTA3NGM0MDFiYjQwZDM1YThkYWNhOWJkMF8xLTAtMS0xLTA_c2af0f4e-ca6e-468f-82b5-4e34e0a2447b">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6ODEyYjM0NzkwNzRjNDAxYmI0MGQzNWE4ZGFjYTliZDAvdGFibGVyYW5nZTo4MTJiMzQ3OTA3NGM0MDFiYjQwZDM1YThkYWNhOWJkMF8xLTEtMS0xLTA_bfe3de01-7d1c-4d22-9327-37971719c0e6">001-36383</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6ODEyYjM0NzkwNzRjNDAxYmI0MGQzNWE4ZGFjYTliZDAvdGFibGVyYW5nZTo4MTJiMzQ3OTA3NGM0MDFiYjQwZDM1YThkYWNhOWJkMF8xLTItMS0xLTA_2633dae9-a31b-4ed9-9d99-8051f619a984">94-3394123</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8yODk_8f27dedf-3abb-4321-9bb0-d300ffa0b4d8">Bishop Ranch 8</dei:EntityAddressAddressLine1>
    <dei:EntityAddressAddressLine2
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8yOTM_21467ed4-1a0c-47e2-baf1-9d1f6d7272f5">4000 Executive Parkway,</dei:EntityAddressAddressLine2>
    <dei:EntityAddressAddressLine3
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8yOTY_2d5a1276-78ae-4a1c-b728-3f4e73ef722b">Suite 400</dei:EntityAddressAddressLine3>
    <dei:EntityAddressCityOrTown
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8zMDA_0514e752-28f4-40f7-bbbf-eaedc182617f">San Ramon,</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8zMDM_b5f9db71-e20d-40af-87ac-16d3edbbd4d7">CA</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV8zMDY_9ed471fd-8810-49a6-ba63-7004bf2a2921">94583</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV80MTU_fad25b48-2062-470f-a703-19b458bdfb35">925</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGV4dHJlZ2lvbjo2ZjdiOGM3YTZhY2M0Y2MyYmI1ZWRlYTU3NDlmOTEyMV80MTk_0aa4fedd-691a-4060-a841-43a0c7a52928">201-2000</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6ZTg5OTRiMmVhMWZkNGQ1OGE3M2Y2OTE1ZmJlMTY1ZjEvdGFibGVyYW5nZTplODk5NGIyZWExZmQ0ZDU4YTczZjY5MTVmYmUxNjVmMV8wLTAtMS0xLTA_a388459e-9d23-4972-8aec-cdac410284ef">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6YmIwMzU2ODExOWI0NGUyYmFmN2Q5NTQwOWFmOTY1ODMvdGFibGVyYW5nZTpiYjAzNTY4MTE5YjQ0ZTJiYWY3ZDk1NDA5YWY5NjU4M18wLTAtMS0xLTA_beec3df9-ac60-437a-b049-cf388562b29f">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6MWU3ZjVhNGVmOWI4NDg1Y2IzNzUxYTM3Nzc4ZDZlYjQvdGFibGVyYW5nZToxZTdmNWE0ZWY5Yjg0ODVjYjM3NTFhMzc3NzhkNmViNF8wLTAtMS0xLTA_28da5158-6216-46cc-90ce-157b555a18e3">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6OTBhNmViYzFhMzJmNDYwZmE0Mzg0ZDA4ZGZiYWUzYTEvdGFibGVyYW5nZTo5MGE2ZWJjMWEzMmY0NjBmYTQzODRkMDhkZmJhZTNhMV8wLTAtMS0xLTA_04fba5eb-7f5a-41a4-9012-b594b097ece0">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6YzZkMWVlMGMyZDU3NDg5Yjk0Y2U2YzE0MmNhNmVkMzcvdGFibGVyYW5nZTpjNmQxZWUwYzJkNTc0ODliOTRjZTZjMTQyY2E2ZWQzN18xLTAtMS0xLTA_5fe2a889-4ee5-4755-b349-bc40f01b9a81">Common stock, par value $0.001 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6YzZkMWVlMGMyZDU3NDg5Yjk0Y2U2YzE0MmNhNmVkMzcvdGFibGVyYW5nZTpjNmQxZWUwYzJkNTc0ODliOTRjZTZjMTQyY2E2ZWQzN18xLTEtMS0xLTA_2b321653-d752-4f2f-8aca-9f133306816c">FIVN</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6YzZkMWVlMGMyZDU3NDg5Yjk0Y2U2YzE0MmNhNmVkMzcvdGFibGVyYW5nZTpjNmQxZWUwYzJkNTc0ODliOTRjZTZjMTQyY2E2ZWQzN18xLTItMS0xLTA_d78c63c1-b28c-4131-a437-ebe58e2c56d5">NASDAQ</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="i1b60c243691642fbb20e1511af116955_D20200803-20200803"
      id="id3VybDovL2RvY3MudjEvZG9jOjU1ZjBkODlkMzAyNzQxMWE4NWZkOTc1NDRlYThjMTAwL3NlYzo1NWYwZDg5ZDMwMjc0MTFhODVmZDk3NTQ0ZWE4YzEwMF8xL2ZyYWc6NmY3YjhjN2E2YWNjNGNjMmJiNWVkZWE1NzQ5ZjkxMjEvdGFibGU6MzMyNDY5NDcwNzM4NGFlMDgxNDQxMWI0ZjNmYWVhZjYvdGFibGVyYW5nZTozMzI0Njk0NzA3Mzg0YWUwODE0NDExYjRmM2ZhZWFmNl8xLTEtMS0xLTA_2b772a9e-5224-4bb0-8eb5-a784234422ae">false</dei:EntityEmergingGrowthCompany>
</xbrl>
