<?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:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="selb-20211001.xsd" xlink:type="simple"/>
    <context id="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001453687</identifier>
        </entity>
        <period>
            <startDate>2021-10-01</startDate>
            <endDate>2021-10-01</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY180L2ZyYWc6M2U3MmU1NzdkYTYyNGQzM2JlYzRmOTlhMjI3YzI1NDYvdGFibGU6OTJhZWU2MDgzOWQwNGNjY2I3ZGRiZDI5NGQxN2Q2NDMvdGFibGVyYW5nZTo5MmFlZTYwODM5ZDA0Y2NjYjdkZGJkMjk0ZDE3ZDY0M18wLTEtMS0xLTIwNjgw_1763810d-a2f8-4a57-a38c-79693828d9ae">0001453687</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY180L2ZyYWc6M2U3MmU1NzdkYTYyNGQzM2JlYzRmOTlhMjI3YzI1NDYvdGFibGU6OTJhZWU2MDgzOWQwNGNjY2I3ZGRiZDI5NGQxN2Q2NDMvdGFibGVyYW5nZTo5MmFlZTYwODM5ZDA0Y2NjYjdkZGJkMjk0ZDE3ZDY0M18xLTEtMS0xLTIwNjgw_ef3b618c-aef1-4c21-9dec-428a6fa02ec8">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjY0_56f7db8d-b160-419a-b06f-30475380c585">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8yMzQ_79811803-4e46-4020-a85f-827d08c20ea1">2021-10-01</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjY1_6d79edfb-9ae6-4826-a05b-062e4a016801">SELECTA BIOSCIENCES,&#160;INC.</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6OThhNzA3MDBjOTg2NDZmNzk0NGZkNjNiMmI3MTUwNGQvdGFibGVyYW5nZTo5OGE3MDcwMGM5ODY0NmY3OTQ0ZmQ2M2IyYjcxNTA0ZF8wLTAtMS0xLTIwNjgw_a04a42e5-f1e6-4b47-afb4-c99a9085a46c">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6OThhNzA3MDBjOTg2NDZmNzk0NGZkNjNiMmI3MTUwNGQvdGFibGVyYW5nZTo5OGE3MDcwMGM5ODY0NmY3OTQ0ZmQ2M2IyYjcxNTA0ZF8wLTItMS0xLTIwNjgw_d030d99b-cbd8-412f-bf54-963206578f41">001-37798</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6OThhNzA3MDBjOTg2NDZmNzk0NGZkNjNiMmI3MTUwNGQvdGFibGVyYW5nZTo5OGE3MDcwMGM5ODY0NmY3OTQ0ZmQ2M2IyYjcxNTA0ZF8wLTQtMS0xLTIwNjgw_a1641956-4a06-4410-ae2e-3c8c9761e9ed">26-1622110</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjcw_a2a1a28e-7649-4927-b6ca-dd5d7933ce67">65 Grove Street,</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjcx_3a8cc7b0-f998-4e94-9236-f17b5851c522">Watertown,</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjcy_ae096175-dde2-405c-81a7-120dc285ff1e">MA</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjcz_929e4e57-087f-4492-8ea2-4f7a8058ecd6">02472</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjY4_4435e54f-74b9-459c-ad7d-8a0457b4fb26">617</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjY2_c6a35b2e-fb19-44b5-9f38-2b68aa83e3b4">923-1400</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6MjEwZjMyOTYzMDBjNDJlZjg0MDYxMzk2OWFmYWNmZDQvdGFibGVyYW5nZToyMTBmMzI5NjMwMGM0MmVmODQwNjEzOTY5YWZhY2ZkNF8wLTAtMS0xLTIwNjgw_1769a28e-ee51-4ff5-a3ab-63adee69295d">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6MjEwZjMyOTYzMDBjNDJlZjg0MDYxMzk2OWFmYWNmZDQvdGFibGVyYW5nZToyMTBmMzI5NjMwMGM0MmVmODQwNjEzOTY5YWZhY2ZkNF8yLTAtMS0xLTIwNjgw_040f2a92-7e66-4cc5-8ccc-86cd8c987cef">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6MjEwZjMyOTYzMDBjNDJlZjg0MDYxMzk2OWFmYWNmZDQvdGFibGVyYW5nZToyMTBmMzI5NjMwMGM0MmVmODQwNjEzOTY5YWZhY2ZkNF80LTAtMS0xLTIwNjgw_e42fb68e-edc1-485b-90b1-7eed95dea57f">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6MjEwZjMyOTYzMDBjNDJlZjg0MDYxMzk2OWFmYWNmZDQvdGFibGVyYW5nZToyMTBmMzI5NjMwMGM0MmVmODQwNjEzOTY5YWZhY2ZkNF82LTAtMS0xLTIwNjgw_0c13f2bc-e5c8-4139-b23f-bfe878369aef">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6N2Q5YTQ3Y2M5MWU0NGNlM2E3N2Y1NmUxNWNhNjZmMjQvdGFibGVyYW5nZTo3ZDlhNDdjYzkxZTQ0Y2UzYTc3ZjU2ZTE1Y2E2NmYyNF8zLTAtMS0xLTIwNjgw_994ba224-f770-4a29-8a1f-72d64b938b4e">Common Stock, $0.0001 par value per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6N2Q5YTQ3Y2M5MWU0NGNlM2E3N2Y1NmUxNWNhNjZmMjQvdGFibGVyYW5nZTo3ZDlhNDdjYzkxZTQ0Y2UzYTc3ZjU2ZTE1Y2E2NmYyNF8zLTEtMS0xLTIwNjgw_7adf6675-0c67-46fc-839d-7349bd89c132">SELB</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGFibGU6N2Q5YTQ3Y2M5MWU0NGNlM2E3N2Y1NmUxNWNhNjZmMjQvdGFibGVyYW5nZTo3ZDlhNDdjYzkxZTQ0Y2UzYTc3ZjU2ZTE1Y2E2NmYyNF8zLTItMS0xLTIwNjgw_c349bed7-3de1-4528-b9fe-bd37e4bce0a1">NASDAQ</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjY3_b5a17757-ec0b-4900-b0e1-4a7652fbb125">true</dei:EntityEmergingGrowthCompany>
    <dei:EntityExTransitionPeriod
      contextRef="i8f3a17027c5d4040b4a3a45821a250b7_D20211001-20211001"
      id="id3VybDovL2RvY3MudjEvZG9jOmJhMzM5ZTEwMDFjZjQ4YzhhMDMyNGQxZWJmYzM1M2NjL3NlYzpiYTMzOWUxMDAxY2Y0OGM4YTAzMjRkMWViZmMzNTNjY18xL2ZyYWc6NjZmNGM0ZmIxNzBmNGEzNThhOGQzNTgwYTYxYTk5MWUvdGV4dHJlZ2lvbjo2NmY0YzRmYjE3MGY0YTM1OGE4ZDM1ODBhNjFhOTkxZV8xMjY5_2f484f9e-32d7-4b83-bdcb-470712eacc82">true</dei:EntityExTransitionPeriod>
</xbrl>
