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Convertible Debt and Non-Convertible Promissory Notes Notes http://www.alternusce.com/20251231/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes Note 12 - Convertible Debt and Non-Convertible Promissory Notes Notes 23 false false R24.htm 995563 - Disclosure - Note 13 - Other Payables Sheet http://www.alternusce.com/20251231/role/statement-note-13-other-payables Note 13 - Other Payables Notes 24 false false R25.htm 995564 - Disclosure - Note 14 - Leases Sheet http://www.alternusce.com/20251231/role/statement-note-14-leases Note 14 - Leases Notes 25 false false R26.htm 995565 - Disclosure - Note 15 - Commitments and Contingencies Sheet http://www.alternusce.com/20251231/role/statement-note-15-commitments-and-contingencies Note 15 - Commitments and Contingencies Notes 26 false false R27.htm 995566 - Disclosure - Note 16 - Development Cost Sheet http://www.alternusce.com/20251231/role/statement-note-16-development-cost Note 16 - Development Cost Notes 27 false false R28.htm 995567 - Disclosure - Note 17 - Discontinued Operations Sold - Poland and Netherlands Sheet http://www.alternusce.com/20251231/role/statement-note-17-discontinued-operations-sold-poland-and-netherlands Note 17 - Discontinued Operations Sold - Poland and Netherlands Notes 28 false false R29.htm 995568 - Disclosure - Note 18 - Sale of Spanish Subsidiaries Sheet http://www.alternusce.com/20251231/role/statement-note-18-sale-of-spanish-subsidiaries Note 18 - Sale of Spanish Subsidiaries Notes 29 false false R30.htm 995569 - Disclosure - Note 19 - Sale of Assets Held for Sale: MH 02 & its Subsidiaries Sheet http://www.alternusce.com/20251231/role/statement-note-19-sale-of-assets-held-for-sale-mh-02-its-subsidiaries Note 19 - Sale of Assets Held for Sale: MH 02 & its Subsidiaries Notes 30 false false R31.htm 995570 - Disclosure - Note 20 - Shareholders' Equity Sheet http://www.alternusce.com/20251231/role/statement-note-20-shareholders-equity Note 20 - Shareholders' Equity Notes 31 false false R32.htm 995571 - 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Disclosure - Note 3 - Summary of Significant Accounting Policies (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-3-summary-of-significant-accounting-policies-tables Note 3 - Summary of Significant Accounting Policies (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-3-summary-of-significant-accounting-policies 37 false false R38.htm 995580 - Disclosure - Note 4 - Fair Value Measurements (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-4-fair-value-measurements-tables Note 4 - Fair Value Measurements (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-4-fair-value-measurements 38 false false R39.htm 995581 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-tables Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity 39 false false R40.htm 995582 - Disclosure - Note 7 - Prepaid Expenses and Other Current Assets (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-7-prepaid-expenses-and-other-current-assets-tables Note 7 - Prepaid Expenses and Other Current Assets (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-7-prepaid-expenses-and-other-current-assets 40 false false R41.htm 995583 - Disclosure - Note 8 - Capitalized Development Cost and Other Long-term Assets (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-8-capitalized-development-cost-and-other-longterm-assets-tables Note 8 - Capitalized Development Cost and Other Long-term Assets (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-8-capitalized-development-cost-and-other-longterm-assets 41 false false R42.htm 995584 - Disclosure - Note 9 - Accounts Payable (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-9-accounts-payable-tables Note 9 - Accounts Payable (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-9-accounts-payable 42 false false R43.htm 995585 - Disclosure - Note 10 - Accrued Liabilities (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-10-accrued-liabilities-tables Note 10 - Accrued Liabilities (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-10-accrued-liabilities 43 false false R44.htm 995586 - Disclosure - Note 11 - Taxes Recoverable and Payable (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-11-taxes-recoverable-and-payable-tables Note 11 - Taxes Recoverable and Payable (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-11-taxes-recoverable-and-payable 44 false false R45.htm 995587 - Disclosure - Note 12 - Convertible Debt and Non-Convertible Promissory Notes (Tables) Notes http://www.alternusce.com/20251231/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes-tables Note 12 - Convertible Debt and Non-Convertible Promissory Notes (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes 45 false false R46.htm 995588 - Disclosure - Note 14 - Leases (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-14-leases-tables Note 14 - Leases (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-14-leases 46 false false R47.htm 995589 - Disclosure - Note 17 - Discontinued Operations Sold - Poland and Netherlands (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-17-discontinued-operations-sold-poland-and-netherlands-tables Note 17 - Discontinued Operations Sold - Poland and Netherlands (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-17-discontinued-operations-sold-poland-and-netherlands 47 false false R48.htm 995590 - Disclosure - Note 18 - Sale of Spanish Subsidiaries (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-18-sale-of-spanish-subsidiaries-tables Note 18 - Sale of Spanish Subsidiaries (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-18-sale-of-spanish-subsidiaries 48 false false R49.htm 995591 - Disclosure - Note 19 - Sale of Assets Held for Sale: MH 02 & its Subsidiaries (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-19-sale-of-assets-held-for-sale-mh-02-its-subsidiaries-tables Note 19 - Sale of Assets Held for Sale: MH 02 & its Subsidiaries (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-19-sale-of-assets-held-for-sale-mh-02-its-subsidiaries 49 false false R50.htm 995592 - Disclosure - Note 20 - Shareholders' Equity (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-20-shareholders-equity-tables Note 20 - Shareholders' Equity (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-20-shareholders-equity 50 false false R51.htm 995593 - Disclosure - Note 21 - Segment and Geographic Information (Tables) Sheet http://www.alternusce.com/20251231/role/statement-note-21-segment-and-geographic-information-tables Note 21 - Segment and Geographic Information (Tables) Tables http://www.alternusce.com/20251231/role/statement-note-21-segment-and-geographic-information 51 false false R52.htm 995594 - 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Disclosure - Note 3 - Summary of Significant Accounting Policies - Disaggregation of Revenues (Details) Sheet http://www.alternusce.com/20251231/role/statement-note-3-summary-of-significant-accounting-policies-disaggregation-of-revenues-details Note 3 - Summary of Significant Accounting Policies - Disaggregation of Revenues (Details) Details 58 false false R59.htm 995601 - Disclosure - Note 3 - Summary of Significant Accounting Policies - Summary of Antidilutive Securities (Details) Sheet http://www.alternusce.com/20251231/role/statement-note-3-summary-of-significant-accounting-policies-summary-of-antidilutive-securities-details Note 3 - Summary of Significant Accounting Policies - Summary of Antidilutive Securities (Details) Details 59 false false R60.htm 995602 - Disclosure - Note 4 - Fair Value Measurements (Details Textual) Sheet http://www.alternusce.com/20251231/role/statement-note-4-fair-value-measurements-details-textual Note 4 - Fair Value Measurements (Details Textual) Details http://www.alternusce.com/20251231/role/statement-note-4-fair-value-measurements-tables 60 false false R61.htm 995603 - 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/20251231/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 61 false false R62.htm 995604 - Disclosure - Note 4 - Fair Value Measurements - Schedule of Fair Value Assets with Unobservable Inputs (Details) Sheet http://www.alternusce.com/20251231/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 62 false false R63.htm 995605 - Disclosure - Note 4 - Fair Value Measurements - Summary of Fair Value Assumptions (Details) Sheet http://www.alternusce.com/20251231/role/statement-note-4-fair-value-measurements-summary-of-fair-value-assumptions-details Note 4 - Fair Value Measurements - Summary of Fair Value Assumptions (Details) Details 63 false false R64.htm 995606 - Disclosure - Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs (Details) Sheet http://www.alternusce.com/20251231/role/statement-note-4-fair-value-measurements-schedule-of-fair-value-liabilities-with-unobservable-inputs-details Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs (Details) Details 64 false false R65.htm 995607 - Disclosure - Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs (Details) (Parentheticals) Sheet http://www.alternusce.com/20251231/role/statement-note-4-fair-value-measurements-schedule-of-fair-value-liabilities-with-unobservable-inputs-details-parentheticals Note 4 - Fair Value Measurements - Schedule of Fair Value Liabilities With Unobservable Inputs (Details) (Parentheticals) Details 65 false false R66.htm 995608 - Disclosure - Note 5 - LiiON Rescission (Details Textual) Sheet http://www.alternusce.com/20251231/role/statement-note-5-liion-rescission-details-textual Note 5 - LiiON Rescission (Details Textual) Details http://www.alternusce.com/20251231/role/statement-note-5-liion-rescission 66 false false R67.htm 995609 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity (Details Textual) Sheet http://www.alternusce.com/20251231/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-details-textual Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity (Details Textual) Details http://www.alternusce.com/20251231/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-tables 67 false false R68.htm 995610 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Schedule of Consideration Transferred (Details) Sheet http://www.alternusce.com/20251231/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-schedule-of-consideration-transferred-details Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Schedule of Consideration Transferred (Details) Details 68 false false R69.htm 995611 - 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/20251231/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 69 false false R70.htm 995612 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Assets Acquired (Details) Sheet http://www.alternusce.com/20251231/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/20251231/role/statement-note-6-formation-of-everon-energy-joint-venture-and-consolidation-of-variable-interest-entity-tables 70 false false R71.htm 995613 - Disclosure - Note 6 - Formation of EverOn Energy Joint Venture and Consolidation of Variable Interest Entity - Pro Forma Information (Details) Sheet http://www.alternusce.com/20251231/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 71 false false R72.htm 995614 - Disclosure - Note 7 - Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) Sheet http://www.alternusce.com/20251231/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 72 false false R73.htm 995615 - Disclosure - Note 8 - Capitalized Development Cost and Other Long-term Assets (Details Textual) Sheet http://www.alternusce.com/20251231/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/20251231/role/statement-note-8-capitalized-development-cost-and-other-longterm-assets-tables 73 false false R74.htm 995616 - 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/20251231/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 74 false false R75.htm 995617 - Disclosure - Note 9 - Accounts Payable - Schedule of Accounts Payable (Details) Sheet http://www.alternusce.com/20251231/role/statement-note-9-accounts-payable-schedule-of-accounts-payable-details Note 9 - Accounts Payable - Schedule of Accounts Payable (Details) Details 75 false false R76.htm 995618 - Disclosure - Note 10 - Accrued Liabilities - Schedule of Accrued Liabilities (Details) Sheet http://www.alternusce.com/20251231/role/statement-note-10-accrued-liabilities-schedule-of-accrued-liabilities-details Note 10 - Accrued Liabilities - Schedule of Accrued Liabilities (Details) Details 76 false false R77.htm 995619 - Disclosure - Note 11 - Taxes Recoverable and Payable - Schedule of Taxes Recoverable (Details) Sheet http://www.alternusce.com/20251231/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 77 false false R78.htm 995620 - Disclosure - Note 12 - Convertible Debt and Non-Convertible Promissory Notes (Details Textual) Notes http://www.alternusce.com/20251231/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/20251231/role/statement-note-12-convertible-debt-and-nonconvertible-promissory-notes-tables 78 false false R79.htm 995621 - Disclosure - Note 12 - Convertible Debt and Non-Convertible Promissory Notes - 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