<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2023"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:us-gaap="http://fasb.org/us-gaap/2023"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="pmtu-20240927.xsd" xlink:type="simple"/>
    <context id="duration_2024-09-27_to_2024-09-27">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001464423</identifier>
        </entity>
        <period>
            <startDate>2024-09-27</startDate>
            <endDate>2024-09-27</endDate>
        </period>
    </context>
    <context id="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001464423</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:CommonStockMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-09-27</startDate>
            <endDate>2024-09-27</endDate>
        </period>
    </context>
    <context id="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesAPreferredStockMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001464423</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:SeriesAPreferredStockMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-09-27</startDate>
            <endDate>2024-09-27</endDate>
        </period>
    </context>
    <context id="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesBPreferredStockMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001464423</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:SeriesBPreferredStockMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-09-27</startDate>
            <endDate>2024-09-27</endDate>
        </period>
    </context>
    <context id="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesCPreferredStockMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001464423</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:SeriesCPreferredStockMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-09-27</startDate>
            <endDate>2024-09-27</endDate>
        </period>
    </context>
    <context id="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeniorNotesMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001464423</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:SeniorNotesMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-09-27</startDate>
            <endDate>2024-09-27</endDate>
        </period>
    </context>
    <dei:AmendmentFlag contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-307">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="duration_2024-09-27_to_2024-09-27"
      id="Hidden_dei_EntityCentralIndexKey">0001464423</dei:EntityCentralIndexKey>
    <dei:DocumentType contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-358">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-359">2024-09-27</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-360">PennyMac Mortgage Investment Trust</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-361">MD</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-362">001-34416</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-363">27-0186273</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1 contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-364">3043 Townsgate Road</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-365">Westlake Village</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-366">CA</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-367">91361</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-368">(818)</dei:CityAreaCode>
    <dei:LocalPhoneNumber contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-369">224-7442</dei:LocalPhoneNumber>
    <dei:WrittenCommunications contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-370">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-371">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-372">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-373">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember"
      id="ixv-374">Common Shares of Beneficial Interest, $0.01 par value</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember"
      id="ixv-375">PMT</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember"
      id="ixv-376">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesAPreferredStockMember"
      id="ixv-377">8.125% Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, $0.01 par value</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesAPreferredStockMember"
      id="ixv-378">PMT/PA</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesAPreferredStockMember"
      id="ixv-379">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesBPreferredStockMember"
      id="ixv-380">8.00% Series B Cumulative Redeemable Preferred Shares of Beneficial Interest, $0.01 par value</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesBPreferredStockMember"
      id="ixv-381">PMT/PB</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesBPreferredStockMember"
      id="ixv-382">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesCPreferredStockMember"
      id="ixv-383">6.75% Series C Cumulative Redeemable Preferred Shares of Beneficial Interest, $0.01 par value</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesCPreferredStockMember"
      id="ixv-384">PMT/PC</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeriesCPreferredStockMember"
      id="ixv-385">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeniorNotesMember"
      id="ixv-386">8.50% Senior Note Due 2028</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeniorNotesMember"
      id="ixv-387">PMTU</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2024-09-27_to_2024-09-27_us-gaap-StatementClassOfStockAxis_us-gaap-SeniorNotesMember"
      id="ixv-388">NYSE</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany contextRef="duration_2024-09-27_to_2024-09-27" id="ixv-389">false</dei:EntityEmergingGrowthCompany>
</xbrl>
