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Disclosure - Note 27 - Nonconsolidated Variable Interest Entities (Tables) Sheet http://jmpg.com/20191231/role/statement-note-27-nonconsolidated-variable-interest-entities-tables Note 27 - Nonconsolidated Variable Interest Entities (Tables) Tables http://jmpg.com/20191231/role/statement-note-27-nonconsolidated-variable-interest-entities- 55 false false R56.htm 055 - Disclosure - Note 28 - Consolidating Financial Statements (Tables) Sheet http://jmpg.com/20191231/role/statement-note-28-consolidating-financial-statements-tables Note 28 - Consolidating Financial Statements (Tables) Tables http://jmpg.com/20191231/role/statement-note-28-consolidating-financial-statements 56 false false R57.htm 056 - Disclosure - Note 1 - Organization and Description of Business (Details Textual) Sheet http://jmpg.com/20191231/role/statement-note-1-organization-and-description-of-business-details-textual Note 1 - Organization and Description of Business (Details Textual) Details http://jmpg.com/20191231/role/statement-note-1-organization-and-description-of-business-tables 57 false false R58.htm 057 - Disclosure - Note 1 - Organization and Description of Business - Deconsolidation of the CLO's and JMPCA (Details) Sheet http://jmpg.com/20191231/role/statement-note-1-organization-and-description-of-business-deconsolidation-of-the-clos-and-jmpca-details Note 1 - Organization and Description of Business - Deconsolidation of the CLO's and JMPCA (Details) Details 58 false false R59.htm 058 - Disclosure - Note 2 - Summary of Significant Accounting Policies (Details Textual) Sheet http://jmpg.com/20191231/role/statement-note-2-summary-of-significant-accounting-policies-details-textual Note 2 - Summary of Significant Accounting Policies (Details Textual) Details http://jmpg.com/20191231/role/statement-note-2-summary-of-significant-accounting-policies-tables 59 false false R60.htm 059 - Disclosure - Note 2 - Summary of Significant Accounting Policies - Principal Transaction Revenues (Details) Sheet http://jmpg.com/20191231/role/statement-note-2-summary-of-significant-accounting-policies-principal-transaction-revenues-details Note 2 - 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Disclosure - Note 6 - Loans - Loans Collateralizing Asset-Backed Securities Issued, Allowance for Loan Losses (Details) Sheet http://jmpg.com/20191231/role/statement-note-6-loans-loans-collateralizing-assetbacked-securities-issued-allowance-for-loan-losses-details Note 6 - Loans - Loans Collateralizing Asset-Backed Securities Issued, Allowance for Loan Losses (Details) Details 73 false false R74.htm 073 - Disclosure - Note 6 - Loans - Loans Collateralizing Asset-Backed Securities Issued, Schedule of Impaired Financing Receivable (Details) Sheet http://jmpg.com/20191231/role/statement-note-6-loans-loans-collateralizing-assetbacked-securities-issued-schedule-of-impaired-financing-receivable-details Note 6 - Loans - Loans Collateralizing Asset-Backed Securities Issued, Schedule of Impaired Financing Receivable (Details) Details 74 false false R75.htm 074 - Disclosure - Note 6 - Loans - Credit Quality of Loans (Details) Sheet http://jmpg.com/20191231/role/statement-note-6-loans-credit-quality-of-loans-details Note 6 - 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Loans - Loans Held for Investment, Credit Quality of Loans (Details) Details 78 false false R79.htm 078 - Disclosure - Note 7 - Fixed Assets (Details Textual) Sheet http://jmpg.com/20191231/role/statement-note-7-fixed-assets-details-textual Note 7 - Fixed Assets (Details Textual) Details http://jmpg.com/20191231/role/statement-note-7-fixed-assets-tables 79 false false R80.htm 079 - Disclosure - Note 7 - Fixed Assets - Summary of Fixed Assets (Details) Sheet http://jmpg.com/20191231/role/statement-note-7-fixed-assets-summary-of-fixed-assets-details Note 7 - Fixed Assets - Summary of Fixed Assets (Details) Details 80 false false R81.htm 080 - Disclosure - Note 8 - Other Assets and Other Liabilities - Other Assets (Details) Sheet http://jmpg.com/20191231/role/statement-note-8-other-assets-and-other-liabilities-other-assets-details Note 8 - Other Assets and Other Liabilities - Other Assets (Details) Details 81 false false R82.htm 081 - Disclosure - Note 8 - Other Assets and Other Liabilities - Other Liabilities (Details) Sheet http://jmpg.com/20191231/role/statement-note-8-other-assets-and-other-liabilities-other-liabilities-details Note 8 - Other Assets and Other Liabilities - Other Liabilities (Details) Details 82 false false R83.htm 082 - Disclosure - Note 9 - Debt (Details Textual) Sheet http://jmpg.com/20191231/role/statement-note-9-debt-details-textual Note 9 - Debt (Details Textual) Details http://jmpg.com/20191231/role/statement-note-9-debt-tables 83 false false R84.htm 083 - Disclosure - Note 9 - Debt - Debt Issuance Costs (Details) Sheet http://jmpg.com/20191231/role/statement-note-9-debt-debt-issuance-costs-details Note 9 - Debt - Debt Issuance Costs (Details) Details 84 false false R85.htm 084 - Disclosure - Note 9 - Debt - Debt Issuance Costs (Details) (Parentheticals) Sheet http://jmpg.com/20191231/role/statement-note-9-debt-debt-issuance-costs-details-parentheticals Note 9 - Debt - Debt Issuance Costs (Details) (Parentheticals) Details 85 false false R86.htm 085 - Disclosure - Note 9 - Debt - Summary of Scheduled Principal Payments of Debt Obligations (Details) Sheet http://jmpg.com/20191231/role/statement-note-9-debt-summary-of-scheduled-principal-payments-of-debt-obligations-details Note 9 - Debt - Summary of Scheduled Principal Payments of Debt Obligations (Details) Details 86 false false R87.htm 086 - Disclosure - Note 9 - Debt - Notes Payable, Lines of Credit and Credit Facilities (Details) Notes http://jmpg.com/20191231/role/statement-note-9-debt-notes-payable-lines-of-credit-and-credit-facilities-details Note 9 - Debt - Notes Payable, Lines of Credit and Credit Facilities (Details) Details 87 false false R88.htm 087 - Disclosure - Note 9 - Debt - Notes Payable, Lines of Credit and Credit Facilities (Details) (Parentheticals) Notes http://jmpg.com/20191231/role/statement-note-9-debt-notes-payable-lines-of-credit-and-credit-facilities-details-parentheticals Note 9 - Debt - Notes Payable, Lines of Credit and Credit Facilities (Details) (Parentheticals) Details 88 false false R89.htm 088 - Disclosure - Note 10 - Asset-backed Securities Issued (Details Textual) Sheet http://jmpg.com/20191231/role/statement-note-10-assetbacked-securities-issued-details-textual Note 10 - Asset-backed Securities Issued (Details Textual) Details http://jmpg.com/20191231/role/statement-note-10-assetbacked-securities-issued-tables 89 false false R90.htm 089 - Disclosure - Note 10 - Asset-backed Securities Issued - Asset-backed Securities Issued - CLO III, CLO IV, and CLO V (Details) Sheet http://jmpg.com/20191231/role/statement-note-10-assetbacked-securities-issued-assetbacked-securities-issued-clo-iii-clo-iv-and-clo-v-details Note 10 - Asset-backed Securities Issued - Asset-backed Securities Issued - CLO III, CLO IV, and CLO V (Details) Details 90 false false R91.htm 090 - Disclosure - Note 11 - Leases (Details Textual) Sheet http://jmpg.com/20191231/role/statement-note-11-leases-details-textual Note 11 - Leases (Details Textual) Details http://jmpg.com/20191231/role/statement-note-11-leases-tables 91 false false R92.htm 091 - 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