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Statement - Consolidated Statements of Operations and Comprehensive Income / (Loss) (Parentheticals) Sheet http://www.cohencpa.com/20201231/role/statement-consolidated-statements-of-operations-and-comprehensive-income-loss-parentheticals Consolidated Statements of Operations and Comprehensive Income / (Loss) (Parentheticals) Statements 5 false false R6.htm 005 - Statement - Consolidated Statement of Changes in Equity Sheet http://www.cohencpa.com/20201231/role/statement-consolidated-statement-of-changes-in-equity Consolidated Statement of Changes in Equity Statements 6 false false R7.htm 006 - Statement - Consolidated Statements of Cash Flows Sheet http://www.cohencpa.com/20201231/role/statement-consolidated-statements-of-cash-flows- Consolidated Statements of Cash Flows Statements 7 false false R8.htm 007 - Disclosure - Note 1 - Organization and Nature of Operations Sheet http://www.cohencpa.com/20201231/role/statement-note-1-organization-and-nature-of-operations Note 1 - Organization and Nature of Operations Notes 8 false false R9.htm 008 - 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Collateralized Securities Transactions Notes 18 false false R19.htm 018 - Disclosure - Note 12 - Investments in Equity Method Affiliates Sheet http://www.cohencpa.com/20201231/role/statement-note-12-investments-in-equity-method-affiliates Note 12 - Investments in Equity Method Affiliates Notes 19 false false R20.htm 019 - Disclosure - Note 13 - Goodwill Sheet http://www.cohencpa.com/20201231/role/statement-note-13-goodwill Note 13 - Goodwill Notes 20 false false R21.htm 020 - Disclosure - Note 14 - Leases Sheet http://www.cohencpa.com/20201231/role/statement-note-14-leases Note 14 - Leases Notes 21 false false R22.htm 021 - Disclosure - Note 15 - Other Assets Sheet http://www.cohencpa.com/20201231/role/statement-note-15-other-assets- Note 15 - Other Assets Notes 22 false false R23.htm 022 - Disclosure - Note 16 - Furniture, Equipment, and Leasehold Improvements, Net Sheet http://www.cohencpa.com/20201231/role/statement-note-16-furniture-equipment-and-leasehold-improvements-net- Note 16 - 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Equity Notes 28 false false R29.htm 028 - Disclosure - Note 22 - Equity-based Compensation Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation Note 22 - Equity-based Compensation Notes 29 false false R30.htm 029 - Disclosure - Note 23 - Income Taxes Sheet http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes Note 23 - Income Taxes Notes 30 false false R31.htm 030 - Disclosure - Note 24 - Accumulated Other Comprehensive Income/(Loss) Sheet http://www.cohencpa.com/20201231/role/statement-note-24-accumulated-other-comprehensive-incomeloss- Note 24 - Accumulated Other Comprehensive Income/(Loss) Notes 31 false false R32.htm 031 - Disclosure - Note 25 - Net Capital Requirements Sheet http://www.cohencpa.com/20201231/role/statement-note-25-net-capital-requirements Note 25 - Net Capital Requirements Notes 32 false false R33.htm 032 - Disclosure - Note 26 - Earnings (Loss) Per Common Share Sheet http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share Note 26 - Earnings (Loss) Per Common Share Notes 33 false false R34.htm 033 - Disclosure - Note 27 - Reserve Requirements Sheet http://www.cohencpa.com/20201231/role/statement-note-27-reserve-requirements- Note 27 - Reserve Requirements Notes 34 false false R35.htm 034 - Disclosure - Note 28 - Commitments and Contingencies Sheet http://www.cohencpa.com/20201231/role/statement-note-28-commitments-and-contingencies Note 28 - Commitments and Contingencies Notes 35 false false R36.htm 035 - Disclosure - Note 29 - Segment and Geographic Information Sheet http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information Note 29 - Segment and Geographic Information Notes 36 false false R37.htm 036 - Disclosure - Note 30 - Supplemental Cash Flow Disclosure Sheet http://www.cohencpa.com/20201231/role/statement-note-30-supplemental-cash-flow-disclosure- Note 30 - Supplemental Cash Flow Disclosure Notes 37 false false R38.htm 037 - Disclosure - Note 31 - Related Party Transactions Sheet http://www.cohencpa.com/20201231/role/statement-note-31-related-party-transactions- Note 31 - Related Party Transactions Notes 38 false false R39.htm 038 - Disclosure - Note 32 - Due From Due To Related Parties Sheet http://www.cohencpa.com/20201231/role/statement-note-32-due-from-due-to-related-parties Note 32 - Due From Due To Related Parties Notes 39 false false R40.htm 039 - Disclosure - Schedule I Sheet http://www.cohencpa.com/20201231/role/statement-schedule-i- Schedule I Notes 40 false false R41.htm 040 - Disclosure - Selected Quarterly Financial Results (Unaudited) Sheet http://www.cohencpa.com/20201231/role/statement-selected-quarterly-financial-results-unaudited Selected Quarterly Financial Results (Unaudited) Notes 41 false false R42.htm 041 - Disclosure - Significant Accounting Policies (Policies) Sheet http://www.cohencpa.com/20201231/role/statement-significant-accounting-policies-policies Significant Accounting Policies (Policies) Policies http://www.cohencpa.com/20201231/role/statement-note-3-summary-of-significant-accounting-policies 42 false false R43.htm 042 - Disclosure - Note 4 - Insurance SPAC Investments and Other Significant Events (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-4-insurance-spac-investments-and-other-significant-events-tables Note 4 - Insurance SPAC Investments and Other Significant Events (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-4-insurance-spac-investments-and-other-significant-events- 43 false false R44.htm 043 - Disclosure - Note 5 - Net Trading (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-5-net-trading-tables Note 5 - Net Trading (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-5-net-trading 44 false false R45.htm 044 - Disclosure - Note 6 - Receivables from and Payables to Brokers, Dealers, and Clearing Agencies (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-6-receivables-from-and-payables-to-brokers-dealers-and-clearing-agencies-tables Note 6 - Receivables from and Payables to Brokers, Dealers, and Clearing Agencies (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-6-receivables-from-and-payables-to-brokers-dealers-and-clearing-agencies 45 false false R46.htm 045 - Disclosure - Note 7 - Other Receivables (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-7-other-receivables-tables Note 7 - Other Receivables (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-7-other-receivables- 46 false false R47.htm 046 - Disclosure - Note 8 - Financial Instruments (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-8-financial-instruments-tables Note 8 - Financial Instruments (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-8-financial-instruments 47 false false R48.htm 047 - Disclosure - Note 9 - Fair Value Disclosures (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures-tables Note 9 - Fair Value Disclosures (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures 48 false false R49.htm 048 - Disclosure - Note 10 - Derivative Financial Instruments (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-10-derivative-financial-instruments-tables Note 10 - Derivative Financial Instruments (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-10-derivative-financial-instruments 49 false false R50.htm 049 - Disclosure - Note 11 - Collateralized Securities Transactions (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-11-collateralized-securities-transactions-tables Note 11 - Collateralized Securities Transactions (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-11-collateralized-securities-transactions 50 false false R51.htm 050 - Disclosure - Note 12 - Investments in Equity Method Affiliates (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-12-investments-in-equity-method-affiliates-tables Note 12 - Investments in Equity Method Affiliates (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-12-investments-in-equity-method-affiliates 51 false false R52.htm 051 - Disclosure - Note 13 - Goodwill (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-13-goodwill-tables Note 13 - Goodwill (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-13-goodwill 52 false false R53.htm 052 - Disclosure - Note 14 - Leases (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-14-leases-tables Note 14 - Leases (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-14-leases 53 false false R54.htm 053 - Disclosure - Note 15 - Other Assets (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-15-other-assets-tables Note 15 - Other Assets (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-15-other-assets- 54 false false R55.htm 054 - Disclosure - Note 16 - Furniture, Equipment, and Leasehold Improvements, Net (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-16-furniture-equipment-and-leasehold-improvements-net-tables Note 16 - Furniture, Equipment, and Leasehold Improvements, Net (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-16-furniture-equipment-and-leasehold-improvements-net- 55 false false R56.htm 055 - Disclosure - Note 17 - Accounts Payable and Other Liabilities (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-17-accounts-payable-and-other-liabilities-tables Note 17 - Accounts Payable and Other Liabilities (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-17-accounts-payable-and-other-liabilities 56 false false R57.htm 056 - Disclosure - Note 18 - Variable Interest Entities (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-18-variable-interest-entities-tables Note 18 - Variable Interest Entities (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-18-variable-interest-entities 57 false false R58.htm 057 - Disclosure - Note 19 - Redeemable Financial Instruments (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-19-redeemable-financial-instruments-tables Note 19 - Redeemable Financial Instruments (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-19-redeemable-financial-instruments 58 false false R59.htm 058 - Disclosure - Note 20 - Debt (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-20-debt-tables Note 20 - Debt (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-20-debt- 59 false false R60.htm 059 - Disclosure - Note 21 - Equity (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-21-equity-tables Note 21 - Equity (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-21-equity- 60 false false R61.htm 060 - Disclosure - Note 22 - Equity-based Compensation (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-tables Note 22 - Equity-based Compensation (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation 61 false false R62.htm 061 - Disclosure - Note 23 - Income Taxes (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes-tables Note 23 - Income Taxes (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes 62 false false R63.htm 062 - Disclosure - Note 24 - Accumulated Other Comprehensive Income/(Loss) (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-24-accumulated-other-comprehensive-incomeloss-tables Note 24 - Accumulated Other Comprehensive Income/(Loss) (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-24-accumulated-other-comprehensive-incomeloss- 63 false false R64.htm 063 - Disclosure - Note 25 - Net Capital Requirements (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-25-net-capital-requirements-tables Note 25 - Net Capital Requirements (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-25-net-capital-requirements 64 false false R65.htm 064 - Disclosure - Note 26 - Earnings (Loss) Per Common Share (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share-tables Note 26 - Earnings (Loss) Per Common Share (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share 65 false false R66.htm 065 - Disclosure - Note 28 - Commitments and Contingencies (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-28-commitments-and-contingencies-tables Note 28 - Commitments and Contingencies (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-28-commitments-and-contingencies 66 false false R67.htm 066 - Disclosure - Note 29 - Segment and Geographic Information (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information-tables Note 29 - Segment and Geographic Information (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information 67 false false R68.htm 067 - Disclosure - Note 30 - Supplemental Cash Flow Disclosure (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-30-supplemental-cash-flow-disclosure-tables Note 30 - Supplemental Cash Flow Disclosure (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-30-supplemental-cash-flow-disclosure- 68 false false R69.htm 068 - Disclosure - Note 31 - Related Party Transactions (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-31-related-party-transactions-tables Note 31 - Related Party Transactions (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-31-related-party-transactions- 69 false false R70.htm 069 - Disclosure - Note 32 - Due From Due To Related Parties (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-note-32-due-from-due-to-related-parties-tables Note 32 - Due From Due To Related Parties (Tables) Tables http://www.cohencpa.com/20201231/role/statement-note-32-due-from-due-to-related-parties 70 false false R71.htm 070 - Disclosure - Schedule I (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-schedule-i-tables Schedule I (Tables) Tables http://www.cohencpa.com/20201231/role/statement-schedule-i- 71 false false R72.htm 071 - Disclosure - Selected Quarterly Financial Results (Unaudited) (Tables) Sheet http://www.cohencpa.com/20201231/role/statement-selected-quarterly-financial-results-unaudited-tables Selected Quarterly Financial Results (Unaudited) (Tables) Tables http://www.cohencpa.com/20201231/role/statement-selected-quarterly-financial-results-unaudited 72 false false R73.htm 072 - Disclosure - Note 1 - Organization and Nature of Operations (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-1-organization-and-nature-of-operations-details-textual Note 1 - Organization and Nature of Operations (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-1-organization-and-nature-of-operations 73 false false R74.htm 073 - Disclosure - Note 2 - Basis of Presentation (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-2-basis-of-presentation-details-textual Note 2 - Basis of Presentation (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-2-basis-of-presentation 74 false false R75.htm 074 - Disclosure - Note 3 - Summary of Significant Accounting Policies (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-3-summary-of-significant-accounting-policies-details-textual Note 3 - Summary of Significant Accounting Policies (Details Textual) Details 75 false false R76.htm 075 - Disclosure - Note 4 - Insurance SPAC Investments and Other Significant Events (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-4-insurance-spac-investments-and-other-significant-events-details-textual Note 4 - Insurance SPAC Investments and Other Significant Events (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-4-insurance-spac-investments-and-other-significant-events-tables 76 false false R77.htm 076 - Disclosure - Note 4 - Insurance SPAC Investments and Other Significant Events - Income Statement Impact (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-4-insurance-spac-investments-and-other-significant-events-income-statement-impact-details Note 4 - Insurance SPAC Investments and Other Significant Events - Income Statement Impact (Details) Details 77 false false R78.htm 077 - Disclosure - Note 5 - Net Trading - Net Trading (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-5-net-trading-net-trading-details Note 5 - Net Trading - Net Trading (Details) Details 78 false false R79.htm 078 - Disclosure - Note 6 - Receivables from and Payables to Brokers, Dealers, and Clearing Agencies - Receivables from and Payables to from Brokers, Dealers and Clearing Agencies (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-6-receivables-from-and-payables-to-brokers-dealers-and-clearing-agencies-receivables-from-and-payables-to-from-brokers-dealers-and-clearing-agencies-details Note 6 - Receivables from and Payables to Brokers, Dealers, and Clearing Agencies - Receivables from and Payables to from Brokers, Dealers and Clearing Agencies (Details) Details 79 false false R80.htm 079 - Disclosure - Note 7 - Other Receivables - Schedule of Receivables (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-7-other-receivables-schedule-of-receivables-details Note 7 - Other Receivables - Schedule of Receivables (Details) Details 80 false false R81.htm 080 - Disclosure - Note 8 - Financial Instruments - Investments - Trading (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-8-financial-instruments-investments-trading-details Note 8 - Financial Instruments - Investments - Trading (Details) Details 81 false false R82.htm 081 - Disclosure - Note 8 - Financial Instruments - Trading Securities Sold, Not Yet Purchased (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-8-financial-instruments-trading-securities-sold-not-yet-purchased-details Note 8 - Financial Instruments - Trading Securities Sold, Not Yet Purchased (Details) Details 82 false false R83.htm 082 - Disclosure - Note 8 - Financial Instruments - Other Investments, at Fair Value (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-8-financial-instruments-other-investments-at-fair-value-details Note 8 - Financial Instruments - Other Investments, at Fair Value (Details) Details 83 false false R84.htm 083 - Disclosure - Note 9 - Fair Value Disclosures (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures-details-textual Note 9 - Fair Value Disclosures (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures-tables 84 false false R85.htm 084 - Disclosure - Note 9 - Fair Value Disclosures - Fair Value Measurements on a Recurring Basis (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures-fair-value-measurements-on-a-recurring-basis-details Note 9 - Fair Value Disclosures - Fair Value Measurements on a Recurring Basis (Details) Details 85 false false R86.htm 085 - Disclosure - Note 9 - Fair Value Disclosures - Level 3 Rollforward (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures-level-3-rollforward-details Note 9 - Fair Value Disclosures - Level 3 Rollforward (Details) Details 86 false false R87.htm 086 - Disclosure - Note 9 - Fair Value Disclosures - Quantitative Information About Level 3 Fair Value Measurements (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures-quantitative-information-about-level-3-fair-value-measurements-details Note 9 - Fair Value Disclosures - Quantitative Information About Level 3 Fair Value Measurements (Details) Details 87 false false R88.htm 087 - Disclosure - Note 9 - Fair Value Disclosures - Fair Value Measurements of Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-9-fair-value-disclosures-fair-value-measurements-of-investments-in-certain-entities-that-calculate-net-asset-value-per-share-or-its-equivalent-details Note 9 - Fair Value Disclosures - Fair Value Measurements of Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) (Details) Details 88 false false R89.htm 088 - Disclosure - Note 10 - Derivative Financial Instruments (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-10-derivative-financial-instruments-details-textual Note 10 - Derivative Financial Instruments (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-10-derivative-financial-instruments-tables 89 false false R90.htm 089 - Disclosure - Note 10 - Derivative Financial Instruments - Balance Sheet Information (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-10-derivative-financial-instruments-balance-sheet-information-details Note 10 - Derivative Financial Instruments - Balance Sheet Information (Details) Details 90 false false R91.htm 090 - Disclosure - Note 10 - Derivative Financial Instruments - Statement of Operations Information (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-10-derivative-financial-instruments-statement-of-operations-information-details Note 10 - Derivative Financial Instruments - Statement of Operations Information (Details) Details 91 false false R92.htm 091 - Disclosure - Note 11 - Collateralized Securities Transactions (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-11-collateralized-securities-transactions-details-textual Note 11 - Collateralized Securities Transactions (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-11-collateralized-securities-transactions-tables 92 false false R93.htm 092 - Disclosure - Note 11 - Collateralized Securities Transactions - Secured Borrowings (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-11-collateralized-securities-transactions-secured-borrowings-details Note 11 - Collateralized Securities Transactions - Secured Borrowings (Details) Details 93 false false R94.htm 093 - Disclosure - Note 12 - Investments in Equity Method Affiliates (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-12-investments-in-equity-method-affiliates-details-textual Note 12 - Investments in Equity Method Affiliates (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-12-investments-in-equity-method-affiliates-tables 94 false false R95.htm 094 - Disclosure - Note 12 - Investments in Equity Method Affiliates - Investments in Equity Method Affiliates (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-12-investments-in-equity-method-affiliates-investments-in-equity-method-affiliates-details Note 12 - Investments in Equity Method Affiliates - Investments in Equity Method Affiliates (Details) Details 95 false false R96.htm 095 - Disclosure - Note 13 - Goodwill (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-13-goodwill-details-textual Note 13 - Goodwill (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-13-goodwill-tables 96 false false R97.htm 096 - Disclosure - Note 13 - Goodwill - Goodwill (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-13-goodwill-goodwill-details Note 13 - Goodwill - Goodwill (Details) Details 97 false false R98.htm 097 - Disclosure - Note 14 - Leases (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-14-leases-details-textual Note 14 - Leases (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-14-leases-tables 98 false false R99.htm 098 - Disclosure - Note 14 - Leases - Future Maturity of Lease Liabilities (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-14-leases-future-maturity-of-lease-liabilities-details Note 14 - Leases - Future Maturity of Lease Liabilities (Details) Details 99 false false R100.htm 099 - Disclosure - Note 15 - Other Assets - Schedule of Other Assets (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-15-other-assets-schedule-of-other-assets-details Note 15 - Other Assets - Schedule of Other Assets (Details) Details 100 false false R101.htm 100 - Disclosure - Note 16 - Furniture, Equipment, and Leasehold Improvements, Net (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-16-furniture-equipment-and-leasehold-improvements-net-details-textual Note 16 - Furniture, Equipment, and Leasehold Improvements, Net (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-16-furniture-equipment-and-leasehold-improvements-net-tables 101 false false R102.htm 101 - Disclosure - Note 16 - Furniture, Equipment, and Leasehold Improvements, Net - Schedule of Furniture, Equipment, and Leasehold Improvements (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-16-furniture-equipment-and-leasehold-improvements-net-schedule-of-furniture-equipment-and-leasehold-improvements-details Note 16 - Furniture, Equipment, and Leasehold Improvements, Net - Schedule of Furniture, Equipment, and Leasehold Improvements (Details) Details 102 false false R103.htm 102 - Disclosure - Note 17 - Accounts Payable and Other Liabilities - Accounts Payable and Other Liabilities (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-17-accounts-payable-and-other-liabilities-accounts-payable-and-other-liabilities-details Note 17 - Accounts Payable and Other Liabilities - Accounts Payable and Other Liabilities (Details) Details 103 false false R104.htm 103 - Disclosure - Note 18 - Variable Interest Entities (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-18-variable-interest-entities-details-textual Note 18 - Variable Interest Entities (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-18-variable-interest-entities-tables 104 false false R105.htm 104 - Disclosure - Note 18 -Variable Interest Entities - Consolidated VIEs (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-18-variable-interest-entities-consolidated-vies-details Note 18 -Variable Interest Entities - Consolidated VIEs (Details) Details 105 false false R106.htm 105 - Disclosure - Note 18 - Variable Interest Entities - Carrying Value of Variable Interests in Non-consolidated Variable Interest Entities (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-18-variable-interest-entities-carrying-value-of-variable-interests-in-nonconsolidated-variable-interest-entities-details Note 18 - Variable Interest Entities - Carrying Value of Variable Interests in Non-consolidated Variable Interest Entities (Details) Details 106 false false R107.htm 106 - Disclosure - Note 19 - Redeemable Financial Instruments (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-19-redeemable-financial-instruments-details-textual Note 19 - Redeemable Financial Instruments (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-19-redeemable-financial-instruments-tables 107 false false R108.htm 107 - Disclosure - Note 19 - Redeemable Financial Instruments - Redeemable Financial Instruments (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-19-redeemable-financial-instruments-redeemable-financial-instruments-details Note 19 - Redeemable Financial Instruments - Redeemable Financial Instruments (Details) Details 108 false false R109.htm 108 - Disclosure - Note 20 - Debt (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-20-debt-details-textual Note 20 - Debt (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-20-debt-tables 109 false false R110.htm 109 - Disclosure - Note 20 - Debt - Detail of Debt (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-20-debt-detail-of-debt-details Note 20 - Debt - Detail of Debt (Details) Details 110 false false R111.htm 110 - Disclosure - Note 20 - Debt - Interest Expense (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-20-debt-interest-expense-details Note 20 - Debt - Interest Expense (Details) Details 111 false false R112.htm 111 - Disclosure - Note 21 - Equity (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-21-equity-details-textual Note 21 - Equity (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-21-equity-tables 112 false false R113.htm 112 - Disclosure - Note 21 - Equity - Shares Outstanding of Stockholders' Equity of the Company (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-21-equity-shares-outstanding-of-stockholders-equity-of-the-company-details Note 21 - Equity - Shares Outstanding of Stockholders' Equity of the Company (Details) Details 113 false false R114.htm 113 - Disclosure - Note 21 - Equity - Rollforward of Units Outstanding (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-21-equity-rollforward-of-units-outstanding-details Note 21 - Equity - Rollforward of Units Outstanding (Details) Details 114 false false R115.htm 114 - Disclosure - Note 21 - Equity - Schedule of Effects of Changes in Ownership Interest Subsidiary (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-21-equity-schedule-of-effects-of-changes-in-ownership-interest-subsidiary-details Note 21 - Equity - Schedule of Effects of Changes in Ownership Interest Subsidiary (Details) Details 115 false false R116.htm 115 - Disclosure - Note 21 - Equity - Rollforward of Non-controlled Interests (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-21-equity-rollforward-of-noncontrolled-interests-details Note 21 - Equity - Rollforward of Non-controlled Interests (Details) Details 116 false false R117.htm 116 - Disclosure - Note 22 - Equity-based Compensation (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-details-textual Note 22 - Equity-based Compensation (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-tables 117 false false R118.htm 117 - Disclosure - Note 22 - Equity-based Compensation - Equity-based Compensation Included in Compensation and Benefits (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-equitybased-compensation-included-in-compensation-and-benefits-details Note 22 - Equity-based Compensation - Equity-based Compensation Included in Compensation and Benefits (Details) Details 118 false false R119.htm 118 - Disclosure - Note 22 - Equity-based Compensation - Detail of Equity Based Compensation by Plan (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-detail-of-equity-based-compensation-by-plan-details Note 22 - Equity-based Compensation - Detail of Equity Based Compensation by Plan (Details) Details 119 false false R120.htm 119 - Disclosure - Note 22 - Equity-based Compensation - Restricted Stock (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-restricted-stock-details Note 22 - Equity-based Compensation - Restricted Stock (Details) Details 120 false false R121.htm 120 - Disclosure - Note 22 - Equity-based Compensation - Service based Vesting (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-service-based-vesting-details Note 22 - Equity-based Compensation - Service based Vesting (Details) Details 121 false false R122.htm 121 - Disclosure - Note 22 - Equity-based Compensation Performance Based Vesting (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-22-equitybased-compensation-performance-based-vesting-details Note 22 - Equity-based Compensation Performance Based Vesting (Details) Details 122 false false R123.htm 122 - Disclosure - Note 23 - Income Taxes (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes-details-textual Note 23 - Income Taxes (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes-tables 123 false false R124.htm 123 - Disclosure - Note 23 - Income Taxes - Income Tax Expense (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes-income-tax-expense-details Note 23 - Income Taxes - Income Tax Expense (Details) Details 124 false false R125.htm 124 - Disclosure - Note 23 - Income Taxes - Income (Loss) Before Income Taxes (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes-income-loss-before-income-taxes-details Note 23 - Income Taxes - Income (Loss) Before Income Taxes (Details) Details 125 false false R126.htm 125 - Disclosure - Note 23 - Income Taxes - Income Tax Rate Reconciliation (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes-income-tax-rate-reconciliation-details Note 23 - Income Taxes - Income Tax Rate Reconciliation (Details) Details 126 false false R127.htm 126 - Disclosure - Note 23 - Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-23-income-taxes-schedule-of-deferred-tax-assets-and-liabilities-details Note 23 - Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) Details 127 false false R128.htm 127 - Disclosure - Note 24 - Accumulated Other Comprehensive Income (Loss) - Accumulated Other Comprehensive Income/(Loss) (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-24-accumulated-other-comprehensive-income-loss-accumulated-other-comprehensive-incomeloss-details Note 24 - Accumulated Other Comprehensive Income (Loss) - Accumulated Other Comprehensive Income/(Loss) (Details) Details http://www.cohencpa.com/20201231/role/statement-note-24-accumulated-other-comprehensive-incomeloss-tables 128 false false R129.htm 128 - Disclosure - Note 25 - Net Capital Requirements - Statutory Net Capital Requirements (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-25-net-capital-requirements-statutory-net-capital-requirements-details Note 25 - Net Capital Requirements - Statutory Net Capital Requirements (Details) Details 129 false false R130.htm 129 - Disclosure - Note 26 - Earnings (Loss) Per Common Share (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share-details-textual Note 26 - Earnings (Loss) Per Common Share (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share-tables 130 false false R131.htm 130 - Disclosure - Note 26 - Earnings (Loss) Per Common Share- Earnings (Loss) Per Common Share (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share-earnings-loss-per-common-share-details Note 26 - Earnings (Loss) Per Common Share- Earnings (Loss) Per Common Share (Details) Details http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share-tables 131 false false R132.htm 131 - Disclosure - Note 26 - Earnings (Loss) Per Common Share - Schedule of Anti-Dilutive Securities (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share-schedule-of-antidilutive-securities-details Note 26 - Earnings (Loss) Per Common Share - Schedule of Anti-Dilutive Securities (Details) Details http://www.cohencpa.com/20201231/role/statement-note-26-earnings-loss-per-common-share-tables 132 false false R133.htm 132 - Disclosure - Note 28 - Commitments and Contingencies (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-28-commitments-and-contingencies-details-textual Note 28 - Commitments and Contingencies (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-28-commitments-and-contingencies-tables 133 false false R134.htm 133 - Disclosure - Note 28 - Comments and Contingencies - Future Lease Commitments (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-28-comments-and-contingencies-future-lease-commitments-details Note 28 - Comments and Contingencies - Future Lease Commitments (Details) Details 134 false false R135.htm 134 - Disclosure - Note 29 - Segment and Geographic Information (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information-details-textual Note 29 - Segment and Geographic Information (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information-tables 135 false false R136.htm 135 - Disclosure - Note 29 - Segment and Geographic Information - Statements of Operations Information (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information-statements-of-operations-information-details Note 29 - Segment and Geographic Information - Statements of Operations Information (Details) Details 136 false false R137.htm 136 - Disclosure - Note 29 - Segment and Geographic Information - Balance Sheet Data (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information-balance-sheet-data-details Note 29 - Segment and Geographic Information - Balance Sheet Data (Details) Details 137 false false R138.htm 137 - Disclosure - Note 29 - Segment and Geographic Information - Geographic Data (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-29-segment-and-geographic-information-geographic-data-details Note 29 - Segment and Geographic Information - Geographic Data (Details) Details 138 false false R139.htm 138 - Disclosure - Note 30 - Supplemental Cash Flow Disclosure (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-30-supplemental-cash-flow-disclosure-details-textual Note 30 - Supplemental Cash Flow Disclosure (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-30-supplemental-cash-flow-disclosure-tables 139 false false R140.htm 139 - Disclosure - Note 30 - Supplemental Cash Flow Disclosure - Collateral Deposits on Cash Flow from Operations (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-30-supplemental-cash-flow-disclosure-collateral-deposits-on-cash-flow-from-operations-details Note 30 - Supplemental Cash Flow Disclosure - Collateral Deposits on Cash Flow from Operations (Details) Details 140 false false R141.htm 140 - Disclosure - Note 31 - Related Party Transactions (Details Textual) Sheet http://www.cohencpa.com/20201231/role/statement-note-31-related-party-transactions-details-textual Note 31 - Related Party Transactions (Details Textual) Details http://www.cohencpa.com/20201231/role/statement-note-31-related-party-transactions-tables 141 false false R142.htm 141 - Disclosure - Note 31 - Related Party Transactions - Routine Transactions Recognized in the Statements of Operations (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-31-related-party-transactions-routine-transactions-recognized-in-the-statements-of-operations-details Note 31 - Related Party Transactions - Routine Transactions Recognized in the Statements of Operations (Details) Details 142 false false R143.htm 142 - Disclosure - Note 32 - Due From Due To Related Parties (Details) Sheet http://www.cohencpa.com/20201231/role/statement-note-32-due-from-due-to-related-parties-details Note 32 - Due From Due To Related Parties (Details) Details http://www.cohencpa.com/20201231/role/statement-note-32-due-from-due-to-related-parties-tables 143 false false R144.htm 143 - Disclosure - Schedule I - Condensed Financial Information of Registrant (Details) Sheet http://www.cohencpa.com/20201231/role/statement-schedule-i-condensed-financial-information-of-registrant-details Schedule I - Condensed Financial Information of Registrant (Details) Details 144 false false R145.htm 144 - Disclosure - Schedule I - Condensed Statements of Operations (Details) Sheet http://www.cohencpa.com/20201231/role/statement-schedule-i-condensed-statements-of-operations-details Schedule I - Condensed Statements of Operations (Details) Details 145 false false R146.htm 145 - Disclosure - Schedule I - Statements of Cash Flows (Details) Sheet http://www.cohencpa.com/20201231/role/statement-schedule-i-statements-of-cash-flows-details Schedule I - Statements of Cash Flows (Details) Details 146 false false R147.htm 146 - Disclosure - Selected Quarterly Financial Results (Unaudited) (Details) Sheet http://www.cohencpa.com/20201231/role/statement-selected-quarterly-financial-results-unaudited-details Selected Quarterly Financial Results (Unaudited) (Details) Details http://www.cohencpa.com/20201231/role/statement-selected-quarterly-financial-results-unaudited-tables 147 false false All Reports Book All Reports cohn-20201231.xml cohn-20201231.xsd cohn-20201231_cal.xml cohn-20201231_def.xml cohn-20201231_lab.xml cohn-20201231_pre.xml http://xbrl.sec.gov/country/2020-01-31 http://fasb.org/srt/2020-01-31 http://fasb.org/us-gaap/2020-01-31 http://xbrl.sec.gov/dei/2019-01-31 true true