Other financial expense Other inflows (outflows) of cash, classified as operating activities Items that are or may be reclassified subsequently to profit or loss Components of other comprehensive income that will be reclassified to profit or loss, net of tax [abstract] Interest income on financial assets held at amortized cost Interest revenue for financial assets measured at amortised cost Income taxes Disclosure of income tax [text block] Acquisition of property, plant and equipment Purchase of property, plant and equipment, classified as investing activities Average price in CHF at beginning of period (in CHF per share) Average price in CHF at end of period (in CHF per share) Weighted average exercise price of other equity instruments outstanding in share-based payment arrangement Share-based compensation Adjustments for share-based payments Proceeds from vesting under the LTI plans Proceeds From Vesting Of Equity Instruments, Net Of Costs Proceeds From Vesting Of Equity Instruments, Net Of Costs Entity File Number Entity File Number Other equity-settled transactions Increase (Decrease) Through Other Equity-Settled Transactions, Equity Increase (Decrease) Through Other Equity-Settled Transactions, Equity Dividends paid, ordinary shares Dividends paid, ordinary shares Disclosure of movements in the number of share options Disclosure of number and weighted average exercise prices of share options [text block] Net foreign exchange loss Net foreign exchange loss (Performance adjustment) (in shares) Number Of Other Equity Instruments Forfeited In Share-Based Payment Arrangement, Non-Market Performance Conditions Not Achieved Number Of Other Equity Instruments Forfeited In Share-Based Payment Arrangement, Non-Market Performance Conditions Not Achieved Total operating expenses Operating expense Weighted average number of shares used in computing basic earnings per share (in shares) Weighted average number of ordinary shares used in calculating basic earnings per share Accrued expenses Current accrued expenses and other current liabilities Number of treasury shares withheld to cover social security and tax liabilities (in shares) Number Of Shares Withheld To Cover Social Security And Tax Liabilities Number Of Shares Withheld To Cover Social Security And Tax Liabilities Disclosure of disaggregation of revenue from contracts with customers [table] Disclosure of disaggregation of revenue from contracts with customers [table] Co-development agreement with Orano Med Co-Development Agreement With Orano Med [Member] Co-development Agreement with Orano Med Disclosure of classes of share capital Disclosure of classes of share capital [text block] Total shareholders' equity Equity at beginning of period Equity at end of period Equity Related party transactions [abstract] Tax loss carryforwards Tax Loss Carryforwards Tax Loss Carryforwards Other comprehensive result Other comprehensive income [abstract] Social security and tax paid on behalf of employees on shares vested under the PSU and RSU program Adjustments For Social Security And Tax Paid On Employee Shares Vested Adjustments For Social Security And Tax Paid On Employee Shares Vested Related parties Disclosure of related party [text block] Net finance result Finance income (cost) Number of treasury shares vested under the program (in shares) (Exercised grants), vested (in shares) Number of other equity instruments exercised or vested in share-based payment arrangement Basis of Preparation Statement of IFRS compliance [text block] Net cash from investing activities Cash flows from (used in) investing activities Net increase (decrease) in cash and cash equivalents Increase (decrease) in cash and cash equivalents after effect of exchange rate changes Change in other current assets Adjustments for decrease (increase) in other current assets Interest expense on leases Interest expense on lease liabilities Statement of changes in equity [line items] Statement of changes in equity [line items] Restructuring Expense [Abstract] Restructuring Expense [Abstract] Accounting estimates and judgments Disclosure of accounting judgements and estimates [text block] Share-based compensation costs Increase (decrease) through share-based payment transactions, equity Proceeds from issuance of shares under LTI plans Proceeds from issue of ordinary shares Proceeds from investments in short term time deposits Proceeds From Investments In Short-Term Time Deposits, Classified As Investing Activities Proceeds From Investments In Short-Term Time Deposits, Classified As Investing Activities PSUs and RSUs Restricted Share Units And Performance Share Units [Member] Restricted Share Units And Performance Share Units Average price in CHF, shares vested under the program (in CHF per share) Weighted average exercise price of other equity instruments exercised or vested in share-based payment arrangement Net cash used in financing activities Cash flows from (used in) financing activities Total TCHF value, shares vested under the program Value Of Other Equity Instruments Exercised Or Vested In Share-Based Payment Arrangement Value Of Other Equity Instruments Exercised Or Vested In Share-Based Payment Arrangement Types of contracts [domain] Types of contracts [domain] Items that will not be reclassified to profit or loss Components of other comprehensive income that will not be reclassified to profit or loss, net of tax [abstract] Financial income Total Finance income Total TCHF value, other equity-settled transactions Value Of Other Equity Instruments Settled In Share-Based Payment Arrangement Value Of Other Equity Instruments Settled In Share-Based Payment Arrangement PSU program Performance Share Units (PSU) Performance Share Units (PSU) [Member] Performance Share Units (PSU) Exchange differences on translating foreign operations Exchange differences on translating foreign operations Other comprehensive income, net of tax, exchange differences on translation of foreign operations Total non-current assets Non-current assets Change in accrued expenses Adjustments For Increase (Decrease) In Accrued Expenses Adjustments For Increase (Decrease) In Accrued Expenses Total current assets Current assets (Expired) (in shares) Number of other equity instruments expired in share-based payment arrangement Other Comprehensive result Disclosure of analysis of other comprehensive income by item [text block] Treasury share reserve Total TCHF value at beginning of period Total TCHF value at end of period Treasury shares Disclosure Of Number And Weighted Average Exercise Prices Of Other Equity Instruments [Line Items] Disclosure Of Number And Weighted Average Exercise Prices Of Other Equity Instruments [Line Items] Disclosure Of Number And Weighted Average Exercise Prices Of Other Equity Instruments [Line Items] Disclosure Of Number Shares under Share Based Compensation Sschemes [Table] Disclosure Of Number And Weighted Average Exercise Prices Of Other Equity Instruments [Table] Disclosure Of Number And Weighted Average Exercise Prices Of Other Equity Instruments [Table] Disclosure of disaggregation of revenue from contracts with customers [line items] Disclosure of disaggregation of revenue from contracts with customers [line items] Disclosure of non-adjusting events after reporting period [abstract] Issuance of Equity Shares [Abstract] Issuance of Equity Shares [Abstract] Issuance of Equity Shares [Abstract] Statement of changes in equity [table] Statement of changes in equity [table] Trade and other payables Trade and other non-current payables Entity Address, Country Entity Address, Country Treasury shares withheld to cover social security and tax Increase (decrease) through treasury share transactions, equity Types of contracts [axis] Types of contracts [axis] Statement of financial position [abstract] Cover [Abstract] Number of positions eliminated Restructuring Activities, Number of Positions Eliminated Restructuring Activities, Number of Positions Eliminated Exercise price (in CHF per share) Weighted average exercise price of other equity instruments exercisable in share-based payment arrangement Exchange gain (loss) on cash positions Effect of exchange rate changes on cash and cash equivalents Interest received Interest received, classified as investing activities Accounting Estimates and Judgments [Abstract] Accounting Estimates and Judgments [Abstract] Net cash used in operating activities Cash flows from (used in) operating activities Current Fiscal Year End Date Current Fiscal Year End Date (Forfeited) (in shares) Number of other equity instruments forfeited in share-based payment arrangement Disclosure of terms and conditions of share-based payment arrangement [line items] Disclosure of terms and conditions of share-based payment arrangement [line items] Dividends [Abstract] Dividends [Abstract] Share-based compensation Disclosure of share-based payment arrangements [text block] Total liabilities Liabilities Total current liabilities Current liabilities Share capital Issued capital Issued capital Other group-wide disclosures Disclosure of revenue [text block] Document Fiscal Year Focus Document Fiscal Year Focus Trade and other receivables Trade and other current receivables Adjustments for: Adjustments to reconcile profit (loss) [abstract] Net result, attributable to shareholders Net result attributable to shareholders Net result Profit (loss) Investments in short term time deposits Purchase Of Investments In Short-Term Time Deposits, Classified As Investing Activities Purchase Of Investments In Short-Term Time Deposits, Classified As Investing Activities Share-Based Payment Arrangement [Abstract] Share-Based Payment Arrangement Number of shares outstanding (in shares) Number of treasury shares outstanding at beginning of period (in shares) Number of treasury shares outstanding at end of period (in shares) Number of shares outstanding Amendment Flag Amendment Flag Average price in CHF, other equity-settled transactions (in CHF per share) Weighted Average Exercise Price Of Other Equity Instruments Settled In Share-Based Payment Arrangement Weighted Average Exercise Price Of Other Equity Instruments Settled In Share-Based Payment Arrangement Average price in CHF, shares withheld to cover social security and tax liabilities (in CHF per share) Weighted Average Exercise Price Of Other Equity Instruments, Shares Withheld To Cover Social Security And Tax Liabilities Shares Withheld To Cover Social Security And Tax Liabilities Weighted Average Exercise Price Of Other Equity Instruments, Shares Withheld To Cover Social Security And Tax Liabilities Shares Withheld To Cover Social Security And Tax Liabilities Components of equity [domain] Components of equity [domain] Additional paid-in capital Additional paid-in capital [member] Restructuring expenses Expense of restructuring activities Expense of restructuring activities Total non-current liabilities Non-current liabilities Income Taxes And Deferred Taxes [Abstract] Income taxes [Abstract] Total comprehensive result, attributable to shareholders Comprehensive income Statement of changes in equity [abstract] Financial expenses Total Finance costs Income tax Adjustments for income tax expense Income taxes Tax expense (income) Cumulative losses Retained earnings Shares Outstanding [Roll Forward] Shares Outstanding [Roll Forward] Shares Outstanding Basis of Preparation Disclosure of material accounting policy information [text block] Exercise of LTI plans Increase (Decrease) Through Vesting Of Equity Instruments, Equity Increase (Decrease) Through Vesting Of Equity Instruments, Equity New or Revised IFRS Standards and Interpretations Disclosure of expected impact of initial application of new standards or interpretations [text block] Short-term time deposits Short-term deposits, not classified as cash equivalents Document Fiscal Period Focus Document Fiscal Period Focus Cumulative losses Retained earnings [member] Changes in working capital: Changes In Working Capital [Abstract] Changes In Working Capital Financial income and expense Disclosure of finance income (cost) [text block] Total assets Assets Property, plant and equipment Property, plant and equipment including right-of-use assets Granted (in shares) Number of other equity instruments granted in share-based payment arrangement Selling, general and administrative expenses Selling, general and administrative expense Document Period End Date Document Period End Date Change in trade and other payables Adjustments for increase (decrease) in trade and other payables Entity Central Index Key Entity Central Index Key Change in trade and other receivables Adjustments for decrease (increase) in trade and other receivables Disclosure of detailed information about financial expense Disclosure Of Detailed Information About Financial Expense [Table Text Block] Disclosure Of Detailed Information About Financial Expense Number of share-based awards outstanding (in shares) Balance outstanding at beginning of period (in shares) Balance outstanding at end of period (in shares) Number of other equity instruments outstanding in share-based payment arrangement Other financial expenses Other finance cost Analysis of income and expense [abstract] Research and development expenses Research and development expense Research and development expense Interest paid on lease liabilities Interest paid, classified as operating activities Total revenues and other income Revenue Earnings per share Disclosure of earnings per share [text block] Trade and other payables Trade and other current payables Shareholders' equity and liabilities Equity and liabilities [abstract] Entity Address, City or Town Entity Address, City or Town Net foreign exchange gain Net foreign exchange gain Remeasurement of net pension liabilities, net of tax Remeasurement of net pension liabilities Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans Document Type Document Type Financial expenses Adjustments for finance costs Share capital Issued capital [member] Exchange gain/(loss) on working capital positions Adjustment For Exchange Gains (Losses) On Working Capital Positions Adjustment For Exchange Gains (Losses) On Working Capital Positions Financial income Adjustments for finance income Number of shares issued and fully paid (in shares) Number of shares issued and fully paid Dividends Disclosure of dividends [text block] Profit or loss [abstract] Lease liability Non-current lease liabilities Disclosure Of General Information [Abstract] Disclosure Of General Information [Abstract] Operating result Profit (loss) from operating activities Lease liability Current lease liabilities Number of treasury shares, other equity-settled transactions (in shares) Number Of Other Equity Instruments Settled In Share-Based Payment Arrangement Number Of Other Equity Instruments Settled In Share-Based Payment Arrangement Intangible assets Intangible assets other than goodwill Total TCHF value, shares withheld to cover social security and tax liabilities Shares Withheld To Cover Social Security And Tax Liabilities, Value Shares Withheld To Cover Social Security And Tax Liabilities, Value Events after the balance sheet date Disclosure of non-adjusting events after reporting period [text block] General Information Disclosure of general information about financial statements [text block] Types of share-based payment arrangements [domain] Types of share-based payment arrangements [domain] Operating expenses Operating Expenses [Abstract] Operating Expenses Entity Address, Address Line One Entity Address, Address Line One Revenues from research and development collaborations Revenue from contracts with customers Earnings per share [abstract] Diluted net result per share (in CHF per share) Diluted earnings (loss) per share Disclosure Of Significant Accounting Policies [Abstract] Accounting Policies [Abstract] Other equity-settled transactions Adjustments For Other Equity-Settled Transactions Adjustments For Other Equity-Settled Transactions Cash and cash equivalents Cash and cash equivalents at January 1 Cash and cash equivalents at June 30, Cash and cash equivalents Components of equity [axis] Components of equity [axis] Employee benefits Non-current provisions for employee benefits Payment of lease liabilities Payments of lease liabilities, classified as financing activities Disclosure of detailed information about financial income Disclosure Of Detailed Information About Financial Income [Table Text Block] Disclosure Of Detailed Information About Financial Income Restricted Share Units (RSU) Restricted share units [member] Restructuring expense Disclosure Of Restructuring Expense [Text Block] Disclosure Of Restructuring Expense Additional paid-in capital Additional paid-in capital Disclosure of terms and conditions of share-based payment arrangement [table] Disclosure of terms and conditions of share-based payment arrangement [table] Change in employee benefits Adjustments for increase (decrease) in employee benefit liabilities Result before income taxes Profit (loss) before tax Other comprehensive result, net of tax Other comprehensive income Assets Assets [abstract] Treasury share reserve Treasury shares Treasury shares [member] Disclosure of weighted average number of shares used in computation Earnings per share [text block] Revised standards [Abstract] Revised standards [Abstract] Total shareholders' equity and liabilities Equity and liabilities Entity Registrant Name Entity Registrant Name Basic net result per share (in CHF per share) Basic earnings (loss) per share Types of share-based payment arrangements [axis] Types of share-based payment arrangements [axis] Depreciation and amortization Adjustments for depreciation and amortisation expense Share capital Disclosure of share capital, reserves and other equity interest [text block] Statement of cash flows [abstract] Weighted average number of shares used in computing diluted earnings per share (in shares) Weighted average number of ordinary shares used in calculating diluted earnings per share Entity Address, Postal Zip Code Entity Address, Postal Zip Code Issuance of new shares under LTI plans Issue of equity Other current assets Other current assets Revenues and other income Revenue [abstract]