<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xml:lang="en-US"
  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="dbx-20210323.xsd" xlink:type="simple"/>
    <context id="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001467623</identifier>
        </entity>
        <period>
            <startDate>2021-03-23</startDate>
            <endDate>2021-03-23</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl80L2ZyYWc6MDYzNDY1ZGRkMmM5NDU2MWE5MzY5ZjkxNTA3NzNhMmYvdGFibGU6ZmNjZTI0ZTlkN2EzNGE4NmJkZGE1OTdkNzNjYjIwZTQvdGFibGVyYW5nZTpmY2NlMjRlOWQ3YTM0YTg2YmRkYTU5N2Q3M2NiMjBlNF8xLTEtMS0xLTA_4da0c8da-91a5-42aa-9cbf-9e96e003dbb6">0001467623</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl80L2ZyYWc6MDYzNDY1ZGRkMmM5NDU2MWE5MzY5ZjkxNTA3NzNhMmYvdGFibGU6ZmNjZTI0ZTlkN2EzNGE4NmJkZGE1OTdkNzNjYjIwZTQvdGFibGVyYW5nZTpmY2NlMjRlOWQ3YTM0YTg2YmRkYTU5N2Q3M2NiMjBlNF8yLTEtMS0xLTA_440d7e1d-2eb4-4912-8eae-f916e4544cad">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzIw_5614d310-2374-466c-8379-a5624f6c7566">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xODA_c65fc0bd-a173-48f1-a5b0-fa31db56d002">2021-03-23</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzI2_3ae2dbf6-6e3e-4015-aa14-8016a3ba56cf">DROPBOX, INC.</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGFibGU6MzJiYTE4ZDA3NzkzNGEzYzkzNjdjMGRiNjAzNmZmMjgvdGFibGVyYW5nZTozMmJhMThkMDc3OTM0YTNjOTM2N2MwZGI2MDM2ZmYyOF8wLTAtMS0xLTA_e0b041d3-a5f8-478e-9d2f-8035c3d9331c">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGFibGU6MzJiYTE4ZDA3NzkzNGEzYzkzNjdjMGRiNjAzNmZmMjgvdGFibGVyYW5nZTozMmJhMThkMDc3OTM0YTNjOTM2N2MwZGI2MDM2ZmYyOF8wLTEtMS0xLTA_4d57682f-4ace-4668-b851-edbcc2a6e991">001-38434</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGFibGU6MzJiYTE4ZDA3NzkzNGEzYzkzNjdjMGRiNjAzNmZmMjgvdGFibGVyYW5nZTozMmJhMThkMDc3OTM0YTNjOTM2N2MwZGI2MDM2ZmYyOF8wLTItMS0xLTA_3de54c83-7d8b-463d-b587-f49e1b7cbf53">26-0138832</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzI3_8e5474cc-0c9c-4eb5-bd8f-f313b5aa86f3">1800 Owens St.</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzIx_bfc39079-a299-4040-81d5-2643ba13d743">San Francisco</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzIy_8d80562e-2176-42ed-88d8-0b6df70f9d72">CA</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzIz_612a5eec-8cc1-424a-859f-0ecd0d401482">94158</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzI0_ecfff6e4-92fb-4829-8b27-c3f296f82747">415</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzI4_1c6d68b2-2a3a-4dcd-862f-816f9d49eda1">857-6800</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzE3_dbbb3c18-20af-40a5-a00c-4aa3e35bb3d3">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzE4_4500c454-1230-4ae7-9fa3-5b00290e58c6">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzE5_b5754bba-1cc6-486a-8ba1-17a8ba2f2536">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzI1_876016df-cac0-4006-ac25-060e46486a80">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGFibGU6MTFkZjVlYzJmZDY2NGYyOThiMWY0NjllOTllN2ZkYjQvdGFibGVyYW5nZToxMWRmNWVjMmZkNjY0ZjI5OGIxZjQ2OWU5OWU3ZmRiNF8yLTEtMS0xLTA_6dfb8759-cba4-42be-ad2e-9557b2b859fc">Class A Common Stock, par value $0.00001 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGFibGU6MTFkZjVlYzJmZDY2NGYyOThiMWY0NjllOTllN2ZkYjQvdGFibGVyYW5nZToxMWRmNWVjMmZkNjY0ZjI5OGIxZjQ2OWU5OWU3ZmRiNF8yLTItMS0xLTA_d6f2c7e7-33f9-4d7b-8940-e2ae56b4361c">DBX</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGFibGU6MTFkZjVlYzJmZDY2NGYyOThiMWY0NjllOTllN2ZkYjQvdGFibGVyYW5nZToxMWRmNWVjMmZkNjY0ZjI5OGIxZjQ2OWU5OWU3ZmRiNF8yLTMtMS0xLTA_cb9a6318-fde1-42f2-88bf-b1ca37152da1">NASDAQ</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="i5cf3348663f0419b8e4b9610bfc3b8e2_D20210323-20210323"
      id="id3VybDovL2RvY3MudjEvZG9jOmIzYzMxNzk3OGZlMjQ5ODc5NGFjYWZhNzM0ZjVkYzdiL3NlYzpiM2MzMTc5NzhmZTI0OTg3OTRhY2FmYTczNGY1ZGM3Yl8xL2ZyYWc6YzU4ODQ0Yjg4MTgyNGRlOWI0N2M5NmFhZDA2ZjdmMTgvdGV4dHJlZ2lvbjpjNTg4NDRiODgxODI0ZGU5YjQ3Yzk2YWFkMDZmN2YxOF8xNzI5_cb3c89cf-6b3c-4923-886e-8e84e8534cd3">false</dei:EntityEmergingGrowthCompany>
</xbrl>
