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Disclosure - Note 4 - Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-4-fair-value-measurements-summary-of-assets-and-liabilities-measured-at-fair-value-on-a-recurring-basis-details Note 4 - Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) Details 94 false false R95.htm 094 - Disclosure - Note 4 - Fair Value Measurements - Schedule of Fair Value Assets with Unobservable Inputs (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-4-fair-value-measurements-schedule-of-fair-value-assets-with-unobservable-inputs-details Note 4 - Fair Value Measurements - Schedule of Fair Value Assets with Unobservable Inputs (Details) Details 95 false false R96.htm 095 - Disclosure - Note 4 - Fair Value Measurements - Summary of Fair Value Assumptions (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-4-fair-value-measurements-summary-of-fair-value-assumptions-details Note 4 - 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Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Schedule of Consideration Transferred (Details) Details 101 false false R102.htm 101 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Schedule of Consideration Transferred (Details) (Parentheticals) Sheet http://www.alternusce.com/20260331/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-schedule-of-consideration-transferred-details-parentheticals Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Schedule of Consideration Transferred (Details) (Parentheticals) Details 102 false false R103.htm 102 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Assets Acquired (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-assets-acquired-details Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Assets Acquired (Details) Details http://www.alternusce.com/20260331/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-tables 103 false false R104.htm 103 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Pro Forma Information (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-pro-forma-information-details Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Pro Forma Information (Details) Details 104 false false R105.htm 104 - Disclosure - Note 7 - Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-7-prepaid-expenses-and-other-current-assets-schedule-of-prepaid-expenses-and-other-current-assets-details Note 7 - Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) Details 105 false false R106.htm 105 - Disclosure - Note 8 - Capitalized Development Cost and Other Long-term Assets (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-8-capitalized-development-cost-and-other-longterm-assets-details-textual Note 8 - Capitalized Development Cost and Other Long-term Assets (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-8-capitalized-development-cost-and-other-longterm-assets-tables 106 false false R107.htm 106 - Disclosure - Note 8 - Capitalized Development Cost and Other Long-term Assets - Schedule of Capitalized Development Costs and Other Long-Term Assets (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-8-capitalized-development-cost-and-other-longterm-assets-schedule-of-capitalized-development-costs-and-other-longterm-assets-details Note 8 - Capitalized Development Cost and Other Long-term Assets - Schedule of Capitalized Development Costs and Other Long-Term Assets (Details) Details 107 false false R108.htm 107 - Disclosure - Note 9 - Accounts Payable - Schedule of Accounts Payable (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-9-accounts-payable-schedule-of-accounts-payable-details Note 9 - Accounts Payable - Schedule of Accounts Payable (Details) Details 108 false false R109.htm 108 - Disclosure - Note 10 - Accrued Liabilities - Schedule of Accrued Liabilities (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-10-accrued-liabilities-schedule-of-accrued-liabilities-details Note 10 - Accrued Liabilities - Schedule of Accrued Liabilities (Details) Details 109 false false R110.htm 109 - Disclosure - Note 11 - Taxes Recoverable and Payable - Schedule of Taxes Recoverable (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-11-taxes-recoverable-and-payable-schedule-of-taxes-recoverable-details Note 11 - Taxes Recoverable and Payable - Schedule of Taxes Recoverable (Details) Details 110 false false R111.htm 110 - Disclosure - Note 12 - Convertible Debt and Non-Convertible Promissory Notes (Details Textual) Notes http://www.alternusce.com/20260331/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes-details-textual Note 12 - Convertible Debt and Non-Convertible Promissory Notes (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes-tables 111 false false R112.htm 111 - Disclosure - Note 12 - Convertible Debt and Non-Convertible Promissory Notes - Convertible Notes (Details) Notes http://www.alternusce.com/20260331/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes-convertible-notes-details Note 12 - Convertible Debt and Non-Convertible Promissory Notes - Convertible Notes (Details) Details 112 false false R113.htm 112 - Disclosure - Note 12 - Convertible Debt and Non-Convertible Promissory Notes - Schedule of Debt (Details) Notes http://www.alternusce.com/20260331/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes-schedule-of-debt-details Note 12 - Convertible Debt and Non-Convertible Promissory Notes - Schedule of Debt (Details) Details 113 false false R114.htm 113 - Disclosure - Note 13 - Other Payables (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-13-other-payables-details-textual Note 13 - Other Payables (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-13-other-payables 114 false false R115.htm 114 - Disclosure - Note 14 - Leases (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-14-leases-details-textual Note 14 - Leases (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-14-leases-tables 115 false false R116.htm 115 - Disclosure - Note 14 - Leases - Summary of Operating Lease Components (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-14-leases-summary-of-operating-lease-components-details Note 14 - 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Discontinued Operations Sold - Poland, Netherlands, Solis and Subsidiaries in Romania (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-17-discontinued-operations-sold-poland-netherlands-solis-and-subsidiaries-in-romania-tables 119 false false R120.htm 119 - Disclosure - Note 17 - Discontinued Operations Sold - Poland, Netherlands, Solis and Subsidiaries in Romania - Summary of Disposal Groups (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-17-discontinued-operations-sold-poland-netherlands-solis-and-subsidiaries-in-romania-summary-of-disposal-groups-details Note 17 - Discontinued Operations Sold - Poland, Netherlands, Solis and Subsidiaries in Romania - Summary of Disposal Groups (Details) Details 120 false false R121.htm 120 - Disclosure - Note 17 - Discontinued Operations Sold - Poland, Netherlands, Solis and Subsidiaries in Romania - Summary of Disposal Groups (Details) (Parentheticals) Sheet http://www.alternusce.com/20260331/role/statement-note-17-discontinued-operations-sold-poland-netherlands-solis-and-subsidiaries-in-romania-summary-of-disposal-groups-details-parentheticals Note 17 - Discontinued Operations Sold - Poland, Netherlands, Solis and Subsidiaries in Romania - Summary of Disposal Groups (Details) (Parentheticals) Details 121 false false R122.htm 121 - Disclosure - Note 18 - Sale of Spanish Subsidiaries (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-18-sale-of-spanish-subsidiaries-details-textual Note 18 - Sale of Spanish Subsidiaries (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-18-sale-of-spanish-subsidiaries-tables 122 false false R123.htm 122 - Disclosure - Note 18 - Sale of Spanish Subsidiaries - Summary of Assets and Liabilities in Sale of Subsidiary (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-18-sale-of-spanish-subsidiaries-summary-of-assets-and-liabilities-in-sale-of-subsidiary-details Note 18 - Sale of Spanish Subsidiaries - Summary of Assets and Liabilities in Sale of Subsidiary (Details) Details 123 false false R124.htm 123 - Disclosure - Note 19 - Sale of Assets Held for Sale: MH 02 & its Subsidiaries (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-19-sale-of-assets-held-for-sale-mh-02-its-subsidiaries-details-textual Note 19 - Sale of Assets Held for Sale: MH 02 & its Subsidiaries (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-19-sale-of-assets-held-for-sale-mh-02-its-subsidiaries-tables 124 false false R125.htm 124 - Disclosure - Note 19 - Sale of Assets Held For Sale: MH 02 & Its Subsidiaries - Summary of Assets and Liabilities in Sale of Subsidiary (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-19-sale-of-assets-held-for-sale-mh-02-its-subsidiaries-summary-of-assets-and-liabilities-in-sale-of-subsidiary-details Note 19 - Sale of Assets Held For Sale: MH 02 & Its Subsidiaries - Summary of Assets and Liabilities in Sale of Subsidiary (Details) Details 125 false false R126.htm 125 - Disclosure - Note 20 - Shareholders' Equity (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-20-shareholders-equity-details-textual Note 20 - Shareholders' Equity (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-20-shareholders-equity-tables 126 false false R127.htm 126 - Disclosure - Note 20 - Shareholders' Equity - Summary of Warrant Activity (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-20-shareholders-equity-summary-of-warrant-activity-details Note 20 - Shareholders' Equity - Summary of Warrant Activity (Details) Details 127 false false R128.htm 127 - Disclosure - Note 21 - Segment and Geographic Information (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-21-segment-and-geographic-information-details-textual Note 21 - Segment and Geographic Information (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-21-segment-and-geographic-information-tables 128 false false R129.htm 128 - Disclosure - Note 21 - Segment and Geographic Information - Schedule of Segment Information (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-21-segment-and-geographic-information-schedule-of-segment-information-details Note 21 - Segment and Geographic Information - Schedule of Segment Information (Details) Details 129 false false R130.htm 129 - Disclosure - Note 22 - Income Tax Provision (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-22-income-tax-provision-details-textual Note 22 - Income Tax Provision (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-22-income-tax-provision-tables 130 false false R131.htm 130 - Disclosure - Note 22 - Income Tax Provision - Components of Tax Expense (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-22-income-tax-provision-components-of-tax-expense-details Note 22 - Income Tax Provision - Components of Tax Expense (Details) Details 131 false false R132.htm 131 - Disclosure - Note 22 - Income Tax Provision - Tax Reconciliation (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-22-income-tax-provision-tax-reconciliation-details Note 22 - Income Tax Provision - Tax Reconciliation (Details) Details 132 false false R133.htm 132 - Disclosure - Note 22 - Income Tax Provision - Tax Reconciliation (Details) (Parentheticals) Sheet http://www.alternusce.com/20260331/role/statement-note-22-income-tax-provision-tax-reconciliation-details-parentheticals Note 22 - Income Tax Provision - Tax Reconciliation (Details) (Parentheticals) Details 133 false false R134.htm 133 - Disclosure - Note 22 - Income Tax Provision - Deferred Tax Assets (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-22-income-tax-provision-deferred-tax-assets-details Note 22 - Income Tax Provision - Deferred Tax Assets (Details) Details 134 false false R135.htm 134 - Disclosure - Note 22 - Income Tax Provision - Unrecognized Tax Benefits (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-22-income-tax-provision-unrecognized-tax-benefits-details Note 22 - Income Tax Provision - Unrecognized Tax Benefits (Details) Details 135 false false R136.htm 135 - Disclosure - Note 23 - Related Party (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-23-related-party-details-textual Note 23 - Related Party (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-23-related-party-tables 136 false false R137.htm 136 - Disclosure - Note 23 - Related Party - Related Party Transactions (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-23-related-party-related-party-transactions-details Note 23 - Related Party - Related Party Transactions (Details) Details 137 false false R138.htm 137 - Disclosure - Note 24 - Subsequent Events (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-24-subsequent-events-details-textual Note 24 - Subsequent Events (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-24-subsequent-events 138 false false R139.htm 138 - Disclosure - Note 1 - Organization and Formation 1 (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-1-organization-and-formation-1-details-textual Note 1 - Organization and Formation 1 (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-1-organization-and-formation 139 false false R140.htm 139 - Disclosure - Note 2 - Going Concern and Management's Plans 1 (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-2-going-concern-and-managements-plans-1-details-textual Note 2 - 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Fair Value Measurements - Summary of Fair Value Assumptions 1 (Details) Details 145 false false R146.htm 145 - Disclosure - Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs 1 (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-4-fair-value-measurements-schedule-of-fair-value-liabilities-with-unobservable-inputs-1-details Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs 1 (Details) Details 146 false false R147.htm 146 - Disclosure - Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs 1 (Details) (Parentheticals) Sheet http://www.alternusce.com/20260331/role/statement-note-4-fair-value-measurements-schedule-of-fair-value-liabilities-with-unobservable-inputs-1-details-parentheticals Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs 1 (Details) (Parentheticals) Details 147 false false R148.htm 147 - Disclosure - Note 5 - EverOn Energy Joint Venture and Consolidation of Variable Interest Entity 1 (Details Textual) Sheet http://www.alternusce.com/20260331/role/statement-note-5-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-1-details-textual Note 5 - EverOn Energy Joint Venture and Consolidation of Variable Interest Entity 1 (Details Textual) Details http://www.alternusce.com/20260331/role/statement-note-5-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-1-tables 148 false false R149.htm 148 - Disclosure - Note 5 - EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Assets Acquired 1 (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-5-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-assets-acquired-1-details Note 5 - EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Assets Acquired 1 (Details) Details http://www.alternusce.com/20260331/role/statement-note-5-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-1-tables 149 false false R150.htm 149 - Disclosure - Note 5 - EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Pro Forma Information 1 (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-5-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-pro-forma-information-1-details Note 5 - EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Pro Forma Information 1 (Details) Details 150 false false R151.htm 150 - Disclosure - Note 6 - Other Long-term Assets - Schedule of Capitalized Development Costs and Other Long-Term Assets 1 (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-6-other-longterm-assets-schedule-of-capitalized-development-costs-and-other-longterm-assets-1-details Note 6 - Other Long-term Assets - Schedule of Capitalized Development Costs and Other Long-Term Assets 1 (Details) Details 151 false false R152.htm 151 - Disclosure - Note 7 - Accounts Payable - Schedule of Accounts Payable 1 (Details) Sheet http://www.alternusce.com/20260331/role/statement-note-7-accounts-payable-schedule-of-accounts-payable-1-details Note 7 - 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