<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.20.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>140</ContextCount>
  <ElementCount>303</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>38</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>00090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>00100 - Statement - Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/StatementBalanceSheets</Role>
      <ShortName>Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>00200 - Statement - Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/StatementStatementsOfOperations</Role>
      <ShortName>Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>00300 - Statement - Statements of Changes in Members' Capital</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/StatementStatementsOfChangesInMembersCapital</Role>
      <ShortName>Statements of Changes in Members' Capital</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>00305 - Statement - Statements of Changes in Members' Capital (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/StatementStatementsOfChangesInMembersCapitalParenthetical</Role>
      <ShortName>Statements of Changes in Members' Capital (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>00400 - Statement - Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/StatementStatementsOfCashFlows</Role>
      <ShortName>Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>10101 - Disclosure - Organization and Limited Liability Company Matters</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureOrganizationAndLimitedLiabilityCompanyMatters</Role>
      <ShortName>Organization and Limited Liability Company Matters</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>10201 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>10301 - Disclosure - Notes Receivable, Net</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.atel.com/role/DisclosureNotesReceivableNet</Role>
      <ShortName>Notes Receivable, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>10401 - Disclosure - Equipment Under Operating Leases, Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNet</Role>
      <ShortName>Equipment Under Operating Leases, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>10501 - Disclosure - Allowance for Credit Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureAllowanceForCreditLosses</Role>
      <ShortName>Allowance for Credit Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>10601 - Disclosure - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureRelatedPartyTransactions</Role>
      <ShortName>Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>10701 - Disclosure - Non-Recourse Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureNonRecourseDebt</Role>
      <ShortName>Non-Recourse Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>10801 - Disclosure - Borrowing Facilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureBorrowingFacilities</Role>
      <ShortName>Borrowing Facilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>10901 - Disclosure - Commitments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureCommitments</Role>
      <ShortName>Commitments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>11001 - Disclosure - Members' Capital</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureMembersCapital</Role>
      <ShortName>Members' Capital</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>11101 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>11201 - Disclosure - Global Health Emergency</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureGlobalHealthEmergency</Role>
      <ShortName>Global Health Emergency</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>20202 - Disclosure - Summary of Significant Accounting Policies (Policy)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicy</Role>
      <ShortName>Summary of Significant Accounting Policies (Policy)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>30303 - Disclosure - Notes Receivable, Net (Tables)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.atel.com/role/DisclosureNotesReceivableNetTables</Role>
      <ShortName>Notes Receivable, Net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureNotesReceivableNet</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>30403 - Disclosure - Equipment Under Operating Leases, Net (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetTables</Role>
      <ShortName>Equipment Under Operating Leases, Net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNet</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>30503 - Disclosure - Allowance for Credit Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureAllowanceForCreditLossesTables</Role>
      <ShortName>Allowance for Credit Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureAllowanceForCreditLosses</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>30603 - Disclosure - Related Party Transactions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureRelatedPartyTransactionsTables</Role>
      <ShortName>Related Party Transactions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureRelatedPartyTransactions</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>30703 - Disclosure - Non-Recourse Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureNonRecourseDebtTables</Role>
      <ShortName>Non-Recourse Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureNonRecourseDebt</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>30803 - Disclosure - Borrowing Facilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureBorrowingFacilitiesTables</Role>
      <ShortName>Borrowing Facilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureBorrowingFacilities</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>31003 - Disclosure - Members' Capital (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureMembersCapitalTables</Role>
      <ShortName>Members' Capital (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureMembersCapital</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>31103 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>40101 - Disclosure - Organization and Limited Liability Company Matters (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureOrganizationAndLimitedLiabilityCompanyMattersNarrativeDetails</Role>
      <ShortName>Organization and Limited Liability Company Matters (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureOrganizationAndLimitedLiabilityCompanyMatters</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>40201 - Disclosure - Summary of Significant Accounting Policies (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureSummaryOfSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicy</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>40301 - Disclosure - Notes Receivable, Net (Narrative) (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.atel.com/role/DisclosureNotesReceivableNetNarrativeDetails</Role>
      <ShortName>Notes Receivable, Net (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureNotesReceivableNetTables</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>40302 - Disclosure - Notes Receivable, Net (Minimum Future Payments Receivable) (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.atel.com/role/DisclosureNotesReceivableNetMinimumFuturePaymentsReceivableDetails</Role>
      <ShortName>Notes Receivable, Net (Minimum Future Payments Receivable) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureNotesReceivableNetTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>40303 - Disclosure - Notes Receivable, Net (Initial Direct Costs, Amortization Expense Related to Notes Receivable and Company's Operating and Direct Finance Leases) (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.atel.com/role/DisclosureNotesReceivableNetInitialDirectCostsAmortizationExpenseRelatedToNotesReceivableAndCompanySOperatingAndDirectFinanceLeasesDetails</Role>
      <ShortName>Notes Receivable, Net (Initial Direct Costs, Amortization Expense Related to Notes Receivable and Company's Operating and Direct Finance Leases) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureNotesReceivableNetTables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>40401 - Disclosure - Equipment Under Operating Leases, Net (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetNarrativeDetails</Role>
      <ShortName>Equipment Under Operating Leases, Net (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetTables</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>40402 - Disclosure - Equipment Under Operating Leases, Net (Investment in Leases) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetInvestmentInLeasesDetails</Role>
      <ShortName>Equipment Under Operating Leases, Net (Investment in Leases) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetTables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>40403 - Disclosure - Equipment Under Operating Leases, Net (Property on Operating Leases) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetPropertyOnOperatingLeasesDetails</Role>
      <ShortName>Equipment Under Operating Leases, Net (Property on Operating Leases) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>40404 - Disclosure - Equipment Under Operating Leases, Net (Future Minimum Lease Payments Receivable) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetFutureMinimumLeasePaymentsReceivableDetails</Role>
      <ShortName>Equipment Under Operating Leases, Net (Future Minimum Lease Payments Receivable) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>40405 - Disclosure - Equipment Under Operating Leases, Net (Schedule of Useful Lives of Lease Assets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetScheduleOfUsefulLivesOfLeaseAssetsDetails</Role>
      <ShortName>Equipment Under Operating Leases, Net (Schedule of Useful Lives of Lease Assets) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureEquipmentUnderOperatingLeasesNetTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>40501 - Disclosure - Allowance for Credit Losses (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureAllowanceForCreditLossesNarrativeDetails</Role>
      <ShortName>Allowance for Credit Losses (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureAllowanceForCreditLossesTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>40502 - Disclosure - Allowance for Credit Losses (Financing Receivables by Credit Quality Indicator and by Class) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureAllowanceForCreditLossesFinancingReceivablesByCreditQualityIndicatorAndByClassDetails</Role>
      <ShortName>Allowance for Credit Losses (Financing Receivables by Credit Quality Indicator and by Class) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureAllowanceForCreditLossesTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>40503 - Disclosure - Allowance for Credit Losses (Net Investment in Financing Receivables by Age) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureAllowanceForCreditLossesNetInvestmentInFinancingReceivablesByAgeDetails</Role>
      <ShortName>Allowance for Credit Losses (Net Investment in Financing Receivables by Age) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureAllowanceForCreditLossesTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>40601 - Disclosure - Related Party Transactions (Affiliates Earned Commissions and Billed for Reimbursements Pursuant to Operating Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureRelatedPartyTransactionsAffiliatesEarnedCommissionsAndBilledForReimbursementsPursuantToOperatingAgreementDetails</Role>
      <ShortName>Related Party Transactions (Affiliates Earned Commissions and Billed for Reimbursements Pursuant to Operating Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureRelatedPartyTransactionsTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>40701 - Disclosure - Non-Recourse Debt (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureNonRecourseDebtNarrativeDetails</Role>
      <ShortName>Non-Recourse Debt (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureNonRecourseDebtTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>40702 - Disclosure - Non-Recourse Debt (Future Minimum Payments of Non-Recourse Debt) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureNonRecourseDebtFutureMinimumPaymentsOfNonRecourseDebtDetails</Role>
      <ShortName>Non-Recourse Debt (Future Minimum Payments of Non-Recourse Debt) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureNonRecourseDebtTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>40801 - Disclosure - Borrowing Facilities (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureBorrowingFacilitiesNarrativeDetails</Role>
      <ShortName>Borrowing Facilities (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureBorrowingFacilitiesTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>40802 - Disclosure - Borrowing Facilities (Borrowings Under the Facility) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureBorrowingFacilitiesBorrowingsUnderFacilityDetails</Role>
      <ShortName>Borrowing Facilities (Borrowings Under the Facility) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureBorrowingFacilitiesTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>40901 - Disclosure - Commitments (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureCommitmentsNarrativeDetails</Role>
      <ShortName>Commitments (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureCommitments</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>41001 - Disclosure - Members' Capital (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureMembersCapitalNarrativeDetails</Role>
      <ShortName>Members' Capital (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureMembersCapitalTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>41002 - Disclosure - Members' Capital (Distributions to Other Members) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureMembersCapitalDistributionsToOtherMembersDetails</Role>
      <ShortName>Members' Capital (Distributions to Other Members) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureMembersCapitalTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>41101 - Disclosure - Fair Value Measurements (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureFairValueMeasurementsNarrativeDetails</Role>
      <ShortName>Fair Value Measurements (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureFairValueMeasurementsTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>41102 - Disclosure - Fair Value Measurements (Fair Value, Warrants Measured on Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureFairValueMeasurementsFairValueWarrantsMeasuredOnRecurringBasisDetails</Role>
      <ShortName>Fair Value Measurements (Fair Value, Warrants Measured on Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureFairValueMeasurementsTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>41103 - Disclosure - Fair Value Measurements (Summary of Valuation Techniques and Significant Unobservable Inputs Used) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureFairValueMeasurementsSummaryOfValuationTechniquesAndSignificantUnobservableInputsUsedDetails</Role>
      <ShortName>Fair Value Measurements (Summary of Valuation Techniques and Significant Unobservable Inputs Used) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureFairValueMeasurementsTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="atel-20200331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>41104 - Disclosure - Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atel.com/role/DisclosureFairValueMeasurementsEstimatedFairValuesOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.atel.com/role/DisclosureFairValueMeasurementsTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>atel-20200331.xml</File>
    <File>atel-20200331.xsd</File>
    <File>atel-20200331_cal.xml</File>
    <File>atel-20200331_def.xml</File>
    <File>atel-20200331_lab.xml</File>
    <File>atel-20200331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/us-gaap/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
