Cover [Abstract] Entity Addresses [Table] Entity Addresses [Line Items] Document Type Entity Registrant Name Entity Central Index Key Document Period End Date Document Fiscal Period Focus Document Fiscal Year Focus Amendment Flag Current Fiscal Year End Date Consolidated Balance Sheets Assets [abstract] Assets Non-current assets [abstract] Non-current assets Property, plant and equipment Property, plant and equipment, end of period Property, plant and equipment, beginning of period Property, plant and equipment Right-of-use assets Balance, end of period Balance, beginning of period Right-of-use assets Intangible asset Intangible Assets Intangible asset Non-current restricted cash and cash equivalents Long-term financial assets Non-current assets Total non-current assets Current assets [abstract] Current assets Current prepaid expenses Prepaid expenses Current accrued income including current contract assets Accrued income Other current receivables Other current receivables Current trade receivables Accounts receivable Short-term deposits, not classified as cash equivalents Short-term financial assets Short-term financial assets due in one year or less Cash and cash equivalents Cash and cash equivalents at end of the period Cash and cash equivalents at beginning of period Company's cash position Cash and cash equivalents Current assets Total current assets Assets Total assets SHAREHOLDERS' EQUITY AND LIABILITIES Shareholders' equity and liabilities Shareholders' equity Shareholders' equity Issued capital Share capital Share premium Share premium Treasury shares Treasury shares Reserve of exchange differences on translation Currency translation differences Retained earnings Accumulated losses Equity Balance, end of period Balance, beginning of period Total shareholders' equity Non-current liabilities [abstract] Non-current liabilities Non-current contract liabilities Long-term deferred contract revenue Non-current lease liabilities Long-term lease liabilities Non-current provisions for employee benefits Net employee defined benefit liabilities Non-current liabilities Total non-current liabilities Current liabilities [abstract] Current liabilities Trade and other current payables Trade and other payables Current accrued expenses and other current liabilities Accrued expenses Total Current deferred income other than current contract liabilities Short-term deferred income Current contract liabilities Short-term deferred contract revenue Current lease liabilities Short-term lease liabilities Current liabilities Total current liabilities Liabilities Total liabilities Equity and liabilities Total shareholders' equity and liabilities Consolidated Statements of Income/(Loss) Contract revenues and other operating income Contract revenues and other operating income Revenue from contracts with customers Contract revenue Revenue Total revenue Expenses, Operating [Abstract] Operating expenses Research and development expense Research & development expenses General and administrative expense General & administrative expenses Other operating income (expense) Income from grants Other operating income/(expense), net Operating expense Total operating expenses Profit (loss) from operating activities Operating loss Financial income Financial income Finance income associated with change in fair value of derivative financial assets Finance costs Financial expense Exchange differences Exchange differences, net Finance income (cost) Net financial gains (losses) Finance result, net Income/(loss) before income tax Loss before tax Income tax expense Income tax expense Loss for the period Loss for the period Loss for the period Net loss for the period Loss per share Loss per share: Basic earnings (loss) per share Basic loss per share for the period attributable to equity holders Diluted earnings (loss) per share Diluted loss per share for the period attributable to equity holders Consolidated Statements of Comprehensive Income/(Loss) Items that may be reclassified to income or loss in subsequent periods (net of tax): Items that may be reclassified to income or loss in subsequent periods (net of tax): Other comprehensive income, net of tax, exchange differences on translation of foreign operations Currency translation differences Comprehensive income Total comprehensive loss (net of tax) Consolidated Statements of Changes in Equity Statement of changes in equity [table] Components of equity [axis] Equity [Member] Issued capital [member] Share capital Share Premium [Member] Share premium Treasury shares [Member] Treasury shares Retained earnings [member] Accumulated losses Reserve of exchange differences on translation [member] Currency translation differences Statement of changes in equity [line items] Other comprehensive income Other comprehensive income/(loss) Increase (decrease) through share-based payment transactions, equity Share-based payments The increase (decrease) in equity from sale or issue of treasury shares net of underwriting fees and transaction costs Sale or issue of treasury shares net of underwriting fees and transaction costs Proceeds from sale of treasury shares in public offerings, net of underwriting fees and transaction costs Increase (decrease) through issue of shares to be held as treasury shares, equity Increase (decrease) through issue of shares to be held as treasury shares, equity Issuance of shares to be held as treasury shares Common shares Issuance of shares, net of transaction costs: The increase in equity through the issue of restricted share awards. Issue of Equity, Restricted Share Awards Restricted share awards Increase (decrease) through exercise of options, equity Exercise of options Consolidated Statements of Cash Flows Cash flows from (used in) operating activities [abstract] Operating activities Adjustments to reconcile profit (loss) [abstract] Adjustments to reconcile net loss for the period to net cash flows: Adjustments for depreciation expense Depreciation of property, plant and equipment Adjustments for depreciation expense for right-of-use assets to reconcile profit (loss) to net cash flow from (used in) operating activities. Adjustments for depreciation expense, right-of-use assets Depreciation of right-of-use assets Adjustments for finance income (cost) Finance (income), net Adjustments for share-based payments Share-based compensation expense Adjustments for increase (decrease) in employee benefit liabilities Change in net employee defined benefit liability Adjustments for interest expense Interest expense Changes in working capital [Abstract] Changes in working capital: Adjustments for decrease (increase) in prepaid expenses (Increase)/decrease in prepaid expenses Adjustments for decrease (increase) in accrued income including contract assets (Increase)/decrease in accrued income Adjustments for decrease (increase) in trade accounts receivable (Increase)/decrease in accounts receivable Adjustments for decrease (increase) in other operating receivables (Increase)/decrease in other current receivables Adjustments for increase (decrease) in accrued expenses to reconcile profit (loss) to net cash flow from (used in) operating activities. Adjustments for increase (decrease) in accrued expenses (Decrease)/increase in accrued expenses Adjustments for increase (decrease) in current contract liabilities Adjustments for increase (decrease) in current contract liabilities (Decrease)/increase in deferred contract revenue, short-term Adjustments for increase (decrease) in deferred income other than contract liabilities (Decrease)/increase in deferred income Adjustments for increase (decrease) in trade and other payables (Decrease)/increase in trade and other payables Adjustments for increase (decrease) in non-current contract liabilities Adjustments for increase (decrease) in non-current contract liabilities (Decrease)/increase in deferred contract revenue, long-term Cash flows from (used in) operations Cash from/(used in) operating activities Interest received, classified as operating activities Interest received Interest paid, classified as operating activities Interest paid Finance costs paid, classified as operating activities Finance expenses paid Cash flows from (used in) operating activities Net cash flows from/(used in) operating activities Cash flows from (used in) investing activities [abstract] Investing activities Payments (proceeds) from purchases (sales) of short-term financial assets, classified as investing activities Payments (proceeds) from purchases (sales) of short-term financial assets, classified as investing activities Short-term financial assets, net Purchase of property, plant and equipment, classified as investing activities Purchases of property, plant and equipment The cash outflow or inflow for deposit of rent. Cash Advances for Rent Deposit Rental deposits Cash flows from (used in) investing activities Net cash flows (used in)/provided by investing activities Cash flows from (used in) financing activities [abstract] Financing activities Proceeds from sale of treasury shares in public offerings, net of underwriting fees and transaction costs Proceeds from sale of treasury shares in public offerings, net of underwriting fees and transaction costs Proceeds from sale of treasury shares in public offerings, net of underwriting fees and transaction costs Proceeds from issuance of shares through equity plans, net of transaction costs Proceeds from issuance of shares through equity plans, net of transaction costs Proceeds from issuance of common shares - equity plan, net of transaction costs Payments for share issue costs and stamp duty associated with public offerings, classified as financing activities Payments for share issue costs and stamp duty associated with public offerings Transaction costs and stamp duty associated with the public offerings of common shares previously recorded in Accrued expenses Payments for share issue costs associated with sale of treasury shares in public offerings, classified as financing activities Payments for share issue costs associated with sale of treasury shares in public offerings Transaction costs associated with the sale of treasury shares in public offering previously recorded in Accrued expenses Payments of lease liabilities, classified as financing activities Principal payments of lease obligations Cash flows from (used in) financing activities Net cash flows provided by/(used in) financing activities Increase (decrease) in cash and cash equivalents before effect of exchange rate changes Net increase/(decrease) in cash and cash equivalents Effect of exchange rate changes on cash and cash equivalents Exchange (loss)/gain on cash and cash equivalents Supplemental non-cash activity [Abstract] Supplemental non-cash activity Transaction costs associated with the sale of treasury shares in public offering recorded in Accrued expenses Transaction costs associated with the sale of treasury shares in public offering recorded in Accrued expenses Transaction costs associated with the sale of treasury shares in public offering recorded in Accrued expenses Corporate information The entire disclosure for general information about the entity. Disclosure of general information about the entity explanatory [Text Block] Corporate information Basis of preparation and changes to accounting policies Basis of preparation and changes to the Company's accounting policies Disclosure of basis of preparation and changes to accounting policies Disclosure of basis of preparation and changes to accounting policies [Text Block] Basis of preparation and changes to the Company's accounting policies Disclosure of revenue [text block] Contract revenues and other operating income Disclosure of earnings per share [text block] Loss per share Property, plant and equipment. Disclosure of property, plant and equipment [text block] Property, plant and equipment Right-of-use assets, long-term financial assets and lease liabilities Disclosure of leases [text block] Right-of-use assets, long-term financial assets and lease liabilities Accrued expenses Trade and other payables and accrued expenses Disclosure of accrued expenses and other liabilities [text block] Accrued expenses Intangible assets Disclosure of intangible assets [text block] Intangible assets Prepaid expenses and accrued income Disclosure of prepayments and other assets [text block] Prepaid expenses Cash and cash equivalents and financial assets The disclosure of cash and cash equivalents and short-term deposits not classified as cash equivalents. Disclosure of cash and cash equivalents and short-term deposits not classified as cash equivalents [text block] Cash and cash equivalents and short-term financial assets Accounts receivable Disclosure of trade and other receivables [text block] Accounts receivable Share capital and Treasury shares Share capital and Treasury shares The entire disclosure for share capital and treasury shares Disclosure of share capital and treasury shares [text block] Share capital and Treasury shares Finance income (expense) Finance result, net Disclosure of finance income (cost) [text block] Finance result, net Subsequent events Disclosure of events after reporting period [text block] Subsequent events Summary of material accounting policies Description of accounting policy for functional currency [text block] Functional and reporting currency The description of the entity's accounting policy for judgments that management has made in the process of applying the entity's accounting policies that have the most significant effect on amounts recognized in the financial statements along with information about the assumptions that the entity makes about the future, and other major sources of estimation uncertainty at the end of the reporting period, that have a significant risk of resulting in a material adjustment to the carrying amounts of assets and liabilities within the next year. Description of accounting policy for accounting judgments and estimates [Policy Text Block] Critical judgments and accounting estimates The description of the entity's accounting policy for fair value of financial assets and liabilities. Fair value of financial assets and liabilities [Policy Text Block] Fair value of financial assets and liabilities The description of the entity's accounting policy for changes to accounting policies recently adopted by the entity. Disclosure Of Accounting Policy For Changes In Accounting Policies Recently Adopted [Text Block] Accounting policies, new standards, interpretations and amendments adopted by the Company Disclosure of effect of changes in foreign exchange rates [text block] Schedule of exchange rates used for translation of financial statements Disclosure of revenue from contracts with customers [text block] Schedule of contract revenues Earnings per share [text block] Schedule of earnings per share Disclosure of instruments with potential future dilutive effect not included in calculation of diluted earnings per share [text block] Schedule of antidilutive securities Disclosure of detailed information about property, plant and equipment [text block] Schedule of movement in the net book values of property, plant and equipment Disclosure of quantitative information about right-of-use assets [text block] Schedule of the movements in the net value book value of right-of-use assets The disclosure of right-of-use assets impact on the company's statements of income/(loss) and statements of cash flows. Disclosure of right-of-use assets impact on statements [Text Block] Schedule of impact on condensed consolidated statements of income/(loss) and cash flows Tabular disclosure of information related to the contractual undiscounted cash flows. Schedule of contractual undiscounted cash flows [Table Text Block] Schedule of contractual undiscounted cash flows for lease obligations Tabular disclosure of information related to accrued expenses Schedule of accrued expenses [Table Text Block] Schedule of accrued expenses Disclosure of detailed information about intangible assets [text block] Schedule of net book value of intangible assets Tabular disclosure of cash and cash equivalents and short-term financial assets Schedule of cash and cash equivalents and short-term financial assets [Table Text Block] Schedule of cash and cash equivalents and short-term financial assets The number of unique proprietary platform technologies to discover, design and develop medicines and diagnostics to target misfolded proteins. Number of technology platforms Functional and reporting currency Closing rate, USD 1 Translation rate into CHF Weighted average exchange rate, USD 1 Going Concern [Abstract] Going concern Disclosure of disaggregation of revenue from contracts with customers [table] Types of contracts [axis] Types of contracts [member] This member stands for Anti-Abeta Active Immunotherapy in AD - 2024 agreement Takeda Pharmaceuticals, USA, Inc. Anti-Abeta Active Immunotherapy in AD- 2024 agreement Takeda Pharmaceuticals, USA, Inc. [Member] Takeda Anti-Abeta Active Immunotherapy in AD – 2024 agreement Takeda Pharmaceuticals, USA, Inc. Disclosure of disaggregation of revenue from contracts with customers [line items] Range [axis] Ranges [member] Top of Range [Member] Maximum Performance obligations [axis] Performance obligations [member] The member represents the performance obligations of the license option and the development, CMC and regulatory activities License option and development, CMC and regulatory activities [Member] License option and development, CMC and regulatory activities The member represents the performance obligation of the License option License option [Member] License option The member represents the performance obligations of the development, CMC and regulatory activities Development, CMC and regulatory activities [Member] Development, CMC and regulatory activities Collaborative agreement, upfront payments received Collaborative agreement, upfront payments received Collaborative agreement, potential receivables for option exercise fee and potential development, commercial and sales-based milestones Collaborative agreement, potential receivables for option exercise fee and potential development, commercial and sales-based milestones Period of time that notice is required to be given for cancellation of the collaborative agreement contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Collaborative agreement, Notice of contract termination period Period to provide notice of termination of agreement The number of performance obligations identified applicable to the entity's assessment of a specific contractual arrangement. Number of performance obligations identified Transaction price allocated to remaining performance obligations Transaction price Number of development milestones that may occur prior to option exercise included in transaction price Number of development milestones that may occur prior to option exercise included in transaction price Contract liabilities Deferred revenue Revenue earned from non-repayable sum of money awarded to an entity to carry out a specific purpose as provided in grant agreements. Grant revenue [Member] Grant revenue Disclosure of disaggregation of revenue from contracts with customers [abstract] Contract revenues Basic earnings per share [abstract] Basic income/(loss) per share (EPS) [Abstract] Profit (loss), attributable to ordinary equity holders of parent entity [abstract] Numerator Profit (loss), attributable to ordinary equity holders of parent entity, used in calculating basic earnings per share Net loss attributable to equity holders of the Company Diluted income/(loss) per share (EPS) [Abstract] Weighted average ordinary shares used in calculating basic and diluted earnings per share [abstract] Denominator Weighted average number of ordinary shares used in calculating basic earnings per share Weighted-average number of shares outstanding used to compute EPS basic attributable to equity holders Weighted average number of ordinary shares used in calculating diluted earnings per share Weighted-average number of shares outstanding used to compute EPS diluted attributable to equity holders Disclosure of instruments with potential future dilutive effect not included in calculation of diluted earnings per share [table] Types of antidilutive instruments [axis] Antidilutive instruments [member] Share options [member] Share options issued and outstanding (in-the-money) Restricted share units [member] Restricted share awards subject to future vesting Disclosure of instruments with potential future dilutive effect not included in calculation of diluted earnings per share [line items] Number of instruments that are antidilutive in period presented Disclosure of detailed information about property, plant and equipment [table] Classes of property, plant and equipment [axis] Property, plant and equipment [member] Furniture Furniture IT Equipment IT Equipment This member stands for a class of property, plant and equipment representing laboratory equipment. Laboratory equipment [Member] Lab Equipment Leasehold Improvements Leasehold Improvements Carrying amount, accumulated depreciation, amortization and impairment and gross carrying amount [axis] Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Carrying amount [member] Gross carrying amount [member] Gross Carrying Amount Acquisition Cost Accumulated depreciation and amortisation [member] Accumulated depreciation Accumulated Amortization Disclosure of detailed information about property, plant and equipment [line items] Reconciliation of changes in property, plant and equipment [abstract] Property, plant and equipment: Additions other than through business combinations, property, plant and equipment Additions Depreciation, property, plant and equipment Depreciation expense Disclosure of quantitative information about right-of-use assets [table] Classes of assets [axis] Assets [member] Buildings Buildings Office Equipment Office Equipment Disclosure of quantitative information about right-of-use assets [line items] Disclosure of quantitative information about leases for lessee [abstract] Right-of-use assets and lease liabilities: Weighted average lessee's incremental borrowing rate applied to lease liabilities recognised at date of initial application of IFRS 16 Weighted average incremental borrowing rate Right-of-use leased assets [Abstract] Right-of-use of leased assets: Additions and reassessment Additions and remeasurements Depreciation, right-of-use assets Depreciation Depreciation of right-of-use assets Expense relating to variable lease payments not included in measurement of lease liabilities Variable lease payments that are not included in the measurement of lease obligations Impact on statements of income/(loss) and cash flows [Abstract] Statements of income/(loss) and cash flows Interest expense on lease liabilities Interest expense on lease liabilities Expense relating to short-term leases for which recognition exemption has been used Expense for short-term leases and leases of low value The expense for leases recognized through profit and loss. Expense relating to leases Total Cash outflow for leases Total cash outflow for leases Disclosure of maturity analysis of operating lease payments [table] Maturity [axis] Aggregated time bands [member] Less than one year 1-3 years 1-3 years 3-5 years 3-5 years Disclosure of maturity analysis of operating lease payments [line items] Contractual undiscounted cash flows for lease liabilities [Abstract] Contractual undiscounted cash flows for lease liabilities: Gross lease liabilities Contractual undiscounted cash flows for lease obligations The amount of deposits held in escrow. Escrow deposit, amount Escrow deposits The amount of current accrued expenses. Current Accrued Expenses Accrued Expenses Disclosure of detailed information about intangible assets [table] Classes of intangible assets other than goodwill [axis] Intangible assets other than goodwill [member] This member stands for an intangible asset that is a clinically-validated active vaccine candidate for the treatment of Parkinson's disease. Acquired IPR&D Asset Disclosure of detailed information about intangible assets [line items] Disclosure of intangible assets material to entity [abstract] Cash [abstract] Cash and cash equivalents [Abstract] Miscellaneous current assets [abstract] Proceeds from maturity of short-term financial assets Proceeds from maturity of short-term financial assets Disclosure of financial assets [table] Disclosure of financial assets [line items] Disclosure of classes of share capital [table] Counterparties [axis] Counterparties [member] The member represents AC Immune USA AC Immune USA [Member] AC Immune USA Disclosure of classes of share capital [line items] Number of shares issued during the period Number of shares issued during the period The number of treasury shares sold during the period Number of treasury shares sold during period Proceeds from sale or issue of treasury shares Number of shares in entity held by entity or by its subsidiaries or associates Number of treasury shares outstanding Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items] Finance result, net