<?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/2021"
  xmlns:exch="http://xbrl.sec.gov/exch/2021"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="fds-20220105.xsd" xlink:type="simple"/>
    <context id="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001013237</identifier>
        </entity>
        <period>
            <startDate>2022-01-05</startDate>
            <endDate>2022-01-05</endDate>
        </period>
    </context>
    <context id="ie0395ec9e3914f65841f2b554511a850_D20220105-20220105">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001013237</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:EntityListingsExchangeAxis">exch:XNYS</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-01-05</startDate>
            <endDate>2022-01-05</endDate>
        </period>
    </context>
    <context id="i3e5c1241ff8a4787b568851f3bf4348e_D20220105-20220105">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001013237</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:EntityListingsExchangeAxis">exch:XNAS</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-01-05</startDate>
            <endDate>2022-01-05</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV80L2ZyYWc6NTZjMWY2NjhkNTE3NDQ0MjgyMzlhMWNiYTE2ZmQ0ZGYvdGFibGU6MTdjZDhhMGJkMjE5NDJlYzlmNzZhMzY1NjE2NDUyOTkvdGFibGVyYW5nZToxN2NkOGEwYmQyMTk0MmVjOWY3NmEzNjU2MTY0NTI5OV8yLTEtMS0xLTUzODU3_00cc6d2b-b8fd-4695-b878-31a5b2981629">0001013237</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV80L2ZyYWc6NTZjMWY2NjhkNTE3NDQ0MjgyMzlhMWNiYTE2ZmQ0ZGYvdGFibGU6MTdjZDhhMGJkMjE5NDJlYzlmNzZhMzY1NjE2NDUyOTkvdGFibGVyYW5nZToxN2NkOGEwYmQyMTk0MmVjOWY3NmEzNjU2MTY0NTI5OV8zLTEtMS0xLTUzODU3_ef0cbf34-a909-49c4-8b4e-f25142d214d1">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV8zMjAz_c496f5cb-9852-4d0d-a44a-18451f1e1e5a">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV8yMjQ_0348a479-0fff-4ce8-87ff-760477a9fe65">2022-01-05</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV8yMjc_d5685daf-6656-4d7e-8e0b-442a1d103bcb">FactSet Research Systems Inc.</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6MDI1M2Q5MDdhODgzNDNhZjk1MDA4OGEwNjc4NmI4MDYvdGFibGVyYW5nZTowMjUzZDkwN2E4ODM0M2FmOTUwMDg4YTA2Nzg2YjgwNl8wLTAtMS0xLTUzODU3_1b6a8087-77fc-4eb0-8fc7-2a38f73d63c4">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6MDI1M2Q5MDdhODgzNDNhZjk1MDA4OGEwNjc4NmI4MDYvdGFibGVyYW5nZTowMjUzZDkwN2E4ODM0M2FmOTUwMDg4YTA2Nzg2YjgwNl8wLTItMS0xLTUzODU3_f23eda5d-9de6-44e9-9b88-adde1e7d8d28">1-11869</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6MDI1M2Q5MDdhODgzNDNhZjk1MDA4OGEwNjc4NmI4MDYvdGFibGVyYW5nZTowMjUzZDkwN2E4ODM0M2FmOTUwMDg4YTA2Nzg2YjgwNl8wLTQtMS0xLTUzODU3_335e6b0b-2964-45ba-991b-781fba0eb5a2">13-3362547</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV8zMjA0_5b67b97f-c1c7-47e3-8a80-b1b074d2b5d2">45 Glover Avenue</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV8zMDM_eb30c5ea-cc22-4dc5-990a-975cc10cb8fc">Norwalk</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV8zMDc_b3f6bbf3-d151-476c-b56f-d80b05eee11a">CT</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV8zMjAy_51f35db9-a4ca-4652-92bb-f9c625345470">06850</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV80MjE_f6f059f1-a809-4f49-b209-d4cf267f1758">203</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV80MjU_94f5f1f2-6dbc-4540-92df-e48d2a319e03">810-1000</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ZTkyZTU4ZDNkZDJkNDY1Yzk2YzY1ZWJiNjViODRkODQvdGFibGVyYW5nZTplOTJlNThkM2RkMmQ0NjVjOTZjNjVlYmI2NWI4NGQ4NF8wLTAtMS0xLTUzODU3_e5f3662d-98c3-44ef-b4dc-67e871b26de8">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ZTkyZTU4ZDNkZDJkNDY1Yzk2YzY1ZWJiNjViODRkODQvdGFibGVyYW5nZTplOTJlNThkM2RkMmQ0NjVjOTZjNjVlYmI2NWI4NGQ4NF8xLTAtMS0xLTUzODU3_18bc55d8-e664-4329-845f-54655229a44d">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ZTkyZTU4ZDNkZDJkNDY1Yzk2YzY1ZWJiNjViODRkODQvdGFibGVyYW5nZTplOTJlNThkM2RkMmQ0NjVjOTZjNjVlYmI2NWI4NGQ4NF8yLTAtMS0xLTUzODU3_7a62abd1-fac8-409f-8005-7b161a2fcccd">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ZTkyZTU4ZDNkZDJkNDY1Yzk2YzY1ZWJiNjViODRkODQvdGFibGVyYW5nZTplOTJlNThkM2RkMmQ0NjVjOTZjNjVlYmI2NWI4NGQ4NF8zLTAtMS0xLTUzODU3_9b30f1d8-349a-410b-b5f0-352690737e30">false</dei:PreCommencementIssuerTenderOffer>
    <dei:EntityEmergingGrowthCompany
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGV4dHJlZ2lvbjo3OWNkOTBhNjA1NjY0ZDM0ODgwZGY3NDc0ZmY0MDI4NV84NjY_79ff2174-3e13-4be3-b484-1d5cf7759a73">false</dei:EntityEmergingGrowthCompany>
    <dei:Security12bTitle
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ODZmMTkyNmIzZmQ2NDU2MDg0NjAyMTFiMmQyODI5MGYvdGFibGVyYW5nZTo4NmYxOTI2YjNmZDY0NTYwODQ2MDIxMWIyZDI4MjkwZl8xLTAtMS0xLTUzODU3_d59e81e9-42ae-4e58-bb1d-a6d583e97722">Common Stock, $0.01 Par Value</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="iaa3071fc3eba4478b2d4ec68a73c2c29_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ODZmMTkyNmIzZmQ2NDU2MDg0NjAyMTFiMmQyODI5MGYvdGFibGVyYW5nZTo4NmYxOTI2YjNmZDY0NTYwODQ2MDIxMWIyZDI4MjkwZl8xLTEtMS0xLTUzODU3_db482814-07f6-4c5d-ab63-69440f5bd666">FDS</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="ie0395ec9e3914f65841f2b554511a850_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ODZmMTkyNmIzZmQ2NDU2MDg0NjAyMTFiMmQyODI5MGYvdGFibGVyYW5nZTo4NmYxOTI2YjNmZDY0NTYwODQ2MDIxMWIyZDI4MjkwZl8xLTItMS0xLTUzODU3_eb28d030-e247-4e30-9d90-e4c330612663">NYSE</dei:SecurityExchangeName>
    <dei:SecurityExchangeName
      contextRef="i3e5c1241ff8a4787b568851f3bf4348e_D20220105-20220105"
      id="id3VybDovL2RvY3MudjEvZG9jOjFmY2Y2NjI2NzUxNzRmNGQ5ZjdjNDE1ZDY2ZDc2NWIxL3NlYzoxZmNmNjYyNjc1MTc0ZjRkOWY3YzQxNWQ2NmQ3NjViMV8xL2ZyYWc6NzljZDkwYTYwNTY2NGQzNDg4MGRmNzQ3NGZmNDAyODUvdGFibGU6ODZmMTkyNmIzZmQ2NDU2MDg0NjAyMTFiMmQyODI5MGYvdGFibGVyYW5nZTo4NmYxOTI2YjNmZDY0NTYwODQ2MDIxMWIyZDI4MjkwZl8yLTItMS0xLTUzODU3_01e7075b-1f4b-4faa-888c-a875b366d81f">NASDAQ</dei:SecurityExchangeName>
</xbrl>
