Document and Entity Information [Abstract] Document Information [Table] Document Information [Line Items] Document Type Document Period End Date Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Period Focus Amendment Flag Consolidated Statements of Comprehensive Income Profit or loss [abstract] INCOME STATEMENT Revenue. Revenue Upfront payment recognized Research and development expense Research and development expenses Selling, general and administrative expense Selling, general and administrative expenses Operating expense Operating expenses Profit (loss) from operating activities Operating profit Financial income Total financial income Finance costs Financial expenses Total financial expenses Profit (loss) before tax Net result before tax Net profit before tax Net profit before tax Tax expense (income), continuing operations Corporate tax Corporate tax expense Total tax expense (income) Profit (loss) Net profit Net profit Basic earnings (loss) per share Basic net profit per share Diluted earnings (loss) per share Diluted net profit per share Statement of comprehensive income [abstract] Statement of Comprehensive Income Other comprehensive income [abstract] Other comprehensive income: Components of other comprehensive income that will be reclassified to profit or loss, net of tax [abstract] Amounts which will be re-classified to the income statement: Other comprehensive income, before tax, exchange differences on translation Exchange differences on translation of foreign operations Comprehensive income Total comprehensive income Total comprehensive income Consolidated Balance Sheets Assets [abstract] ASSETS Intangible assets other than goodwill Cost at end of period Cost at beginning of period Intangible assets Property, plant and equipment Cost at end of period Cost at beginning of period Property and equipment Right-of-use assets Balance at December 31 Balance at January 1 Right-of-use assets Trade and other non-current receivables Receivables Non-current receivables Net deferred tax assets Deferred tax assets Investments accounted for using equity method Other investments Non-current assets Total non-current assets Corporate Tax Receivable Corporate Tax Receivable Corporate tax receivable Trade and other current receivables Receivables Current receivables Amount of investments in debt and equity securities which have original maturities over to 90 days, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer. Ifrs Marketable Securities Current Marketable securities Market value Cash and cash equivalents Cash and cash equivalents at the end of the period Cash and cash equivalents at the beginning of the period Cash and cash equivalents Current assets Total current assets Assets Total assets Equity and liabilities [abstract] SHAREHOLDERS' EQUITY AND LIABILITIES Issued capital Share capital, at end of period Share capital, at beginning of period Share capital Share premium Share premium Other reserves Other reserves Retained earnings Retained earnings Equity Balance at end of period Balance at beginning of period Total shareholders' equity Non-current lease liabilities Lease liabilities Non-current Rent deferred income classified as non-current Deferred revenue Other non-current payables Non-current other payables Other payables Non-current liabilities Total non-current liabilities Current lease liabilities Lease liabilities Current Rent deferred income classified as current Deferred revenue Other current payables Current other payables Other payables Current liabilities Total current liabilities Liabilities Total liabilities Equity and liabilities Total shareholders' equity and liabilities Consolidated Statements of Cash Flows Cash flows from (used in) operating activities [abstract] Cash flows from operating activities: The reversal of financial items to the cash flow under operating activities. Reversal Of Financial Items, Net Reversal of financial items, net Adjustments for total non-cash items to reconcile profit (loss) to net cash flow from (used in) operating activities. Total Adjustments For Non Cash Transactions Adjustment for non-cash transactions Total adjustments for non-cash transactions Increase (decrease) in working capital Change in operating assets and liabilities Total changes in working capital The cash flows from (used in) operating activities, which are the principal revenue-producing activities of the entity and other activities before reconciling the financial items. Cash Flow From (Used In) Operating Activities Before Financial Items Cash flows from operating activities before financial items Interest received, classified as operating activities Interest received Adjustments for interest on lease payments to reconcile profit (loss) to net cash flow from (used in) operating activities. Adjustments For Interest On Lease Payments Interest elements of lease payments Interest paid, classified as operating activities Interest paid Adjustments for income tax expense Corporate taxes paid Cash flows from (used in) operating activities Net cash provided by operating activities Cash flows from (used in) investing activities [abstract] Cash flows from investing activities: Purchase of property, plant and equipment, classified as investing activities Investment in tangible assets Purchase of investments other than investments accounted for using equity method Marketable securities bought Proceeds from sales of investments other than investments accounted for using equity method Marketable securities sold Purchase of interests in investments accounted for using equity method Other investments bought Proceeds from sales of investments accounted for using equity method Other investments sold Cash flows from (used in) investing activities Net cash (used in) investing activities Cash flows from (used in) financing activities [abstract] Cash flows from financing activities: Proceeds From Exercise Of Warrants Warrants exercised Payments of lease liabilities, classified as financing activities Principal elements of lease payments The cash outflow to acquire treasury shares. Payments To Acquire Treasury Shares Purchase of treasury shares The cash outflow for withholding taxes on behalf of employees on net settled restricted stock units (RSUs). Payment Of Withholding Taxes On Behalf Of Employees On Net Settled R S Us Payment of withholding taxes on behalf of employees on net settled RSUs Cash flows from (used in) financing activities Net cash provided by (used in) financing activities Increase (decrease) in cash and cash equivalents before effect of exchange rate changes Changes in cash and cash equivalents Effect of exchange rate changes on cash and cash equivalents Exchange rate adjustments Cash and cash equivalents [abstract] Cash and cash equivalents include: Cash Bank deposits Short-term investments, classified as cash equivalents Short-term marketable securities Consolidated Statements of Changes in Equity Statement of changes in equity [table] Components of equity [axis] Equity [member] Issued capital [member] Share premium [Member] Translation reserves Retained Earnings [Member] Statement of changes in equity [line items] Consolidated Statements of Changes in Equity Other comprehensive income Other comprehensive income n/a Transactions With Owners Transactions with owners: Increase (decrease) through exercise of warrants, equity Exercise of warrants Increase (decrease) through share-based payment transactions, equity Share-based compensation expenses The increase (decrease) in equity resulting from net settlement of restricted stock units. Increase Decrease Through Net Settlement Of Restricted Stock Units, Equity Net settlement of RSUs Tax on items recognized directly in equity. Tax On Items Recognized Directly In Equity Tax on items recognized directly in equity Purchase of treasury shares Purchase of treasury shares Purchase of treasury shares No definition available. Basis of Presentation Disclosure of basis of preparation of financial statements [text block] Basis of Presentation No definition available. Results for the Year The entire disclosure for results for the year. Results For Year Text Block Results for the Year No definition available. Operating Assets and Liabilities The entire disclosure for operating assets and liabilities. Operating Assets And Liabilities [Text Block] Operating Assets and Liabilities Financial Instruments Disclosure of financial risk management [text block] Capital Structure, Financial Risk and Related Items No definition. Other Disclosures The entire information of other disclosures. Other Disclosure [Text Block] Other Disclosures Disclosure of significant accounting policies [text block] Nature of the Business and Accounting Policies The description of the entity's accounting policy for recently adopted new accounting standards. New Accounting Standards - Recently Adopted New Accounting Policies and Disclosures The description of the entity's accounting policy for Basis of presentation. Description Of Accounting Policy For Judgments And Estimates [Policy Text Block] Management's Judgements and Estimates under IFRS Disclosure of interests in subsidiaries [text block] Schedule of activities of the subsidiary Disclosure of disaggregation of revenue from contracts with customers [text block] Schedule of revenue by type and collaboration partner under agreements Tabular disclosure for segment disclosures in the financial statements as the group's business activities. Schedule Of Segment Disclosures In Financial Statements [Table Text Block] Schedule of segment disclosures in the financial statements as the group's business activities. Disclosure of staff cost. Disclosure Of Staff Cost [Table Text Block] Schedule of staff cost Tabular disclosure for corporate and deferred Tax. Disclosure Of Corporate And Deferred Tax [Table Text Block] Schedule of corporate and deferred Tax Disclosure of deferred taxes [text block] Schedule of components of the deferred tax asset Disclosure of earnings per share [text block] Schedule of Result Per Share Disclosure of detailed information about property, plant and equipment [table] Classes of property, plant and equipment [axis] Property, plant and equipment [member] Intangible assets other than goodwill [member] Disclosure of detailed information about property, plant and equipment [line items] Property, Plant and Equipment Disclosure of detailed information about intangible assets [text block] Schedule of Intangible Assets Disclosure of property, plant and equipment [text block] Schedule of property, plant and equipment Disclosure of intangible assets with indefinite useful life [text block] Schedule of straight-line basis of useful lives Disclosure of maturity analysis of operating lease payments [text block] Schedule of future minimum payments under our leases Tabular disclosure of other Investments. Schedule Of Other Investments [Table Text Block] Schedule of other Investments Disclosure of trade and other receivables [text block] Schedules of Receivables Disclosure of deferred income [text block] Schedule of deferred revenue Disclosure of trade and other payables [text block] Schedule of other payables Tabular disclosure of marketable securities in foreign currency. Disclosure Of Marketable Securities By Currency [Table Text Block] Schedule of total marketable securities by currency Tabular disclosure of maturity profile of our marketable securities. Disclosure Of Maturity Profile Of Our Marketable Securities [Table Text Block] Schedule of maturity profile of our marketable securities Disclosure of offsetting of financial assets and financial liabilities [text block] Schedule of Financial Assets and Liabilities Tabular disclosure of level 3 reconciliation of assets measured at fair value. Disclosure Of Fair Value Measurement Of Assets, Level 3 Reconciliation [Table Text Block] Schedule of level 3 reconciliation of assets Tabular disclosure of portfolio of marketable securities. Schedule Of Portfolio Of Marketable Securities Schedule of portfolio of marketable securities na Schedule of financial income and expenses Disclosure of fair value measurement of assets [text block] Schedule of marketable securities Disclosure of number and weighted average exercise prices of other equity instruments [text block] Summary of RSUs activity Tabular disclosure of warrants activity. Disclosure Of Warrants Activity [Table Text Block] Summary of warrants activity The disclosure of the number and weighted average exercise prices of warrants. Disclosure Of Number And Weighted Average Exercise Prices Of Warrants [Table Text Block] Schedule of Weighted Average Exercise Prices Of Warrants Tabular disclosure of fair value of each warrant granted. Valuation Assumptions for Warrants Granted [Table Text Block] Schedule of Fair value of each warrant granted Tabular disclosure of Warrants issued and reissued during the period. Disclosure of Warrants Issued and Warrants Reissued Activity [Table Text Block] Schedule of warrants issued and reissued during the period Disclosure of reserves within equity [text block] Schedule of changes in share capital Disclosure of treasury shares [text block] Schedule Of Treasury Shares Tabular disclosure of repurchase of shares. Schedule of Share Repurchases [Table Text Block] Schedule of share repurchases Disclosure of amounts incurred by entity for provision of key management personnel services provided by separate management entities [text block] Summary of remuneration of the Board of Directors and Executive Management The tabular disclosure of amounts incurred by entity for provision of key management personnel . Disclosure of amounts incurred by entity for provision of key management personnel [Table Text Block] Schedule of Remuneration to the Board of Directors Disclosure of information about key management personnel [text block] Schedule of executive compensation Disclosure of auditors' remuneration [text block] Summary of fees to auditors Disclosure of cash flow statement [text block] Summary of adjustments to cash flow statement Number of approved products commercialized by third parties. Number Of Approved Products Commercialized By Third Parties Number of approved products commercialized by third parties Number of approved products jointly commercialized by collaboration partner. Number Of Approved Products Jointly Commercialized With Collaboration Number of approved products jointly commercialized by collaboration partner Disclosure of subsidiaries [table] Legal Entity [Axis] Entity [Domain] Parent Company [Member] Subsidiaries [axis] Entity's total for subsidiaries [member] This member stands for Genmab B.V. Genmab B.V. This member stands for Genmab Holding B.V. Genmab Holding B.V. This member stands for Genmab US, Inc. Genmab US, Inc. This member stands for Genmab K.K. Genmab K.K. Disclosure of subsidiaries [line items] Activities of the subsidiary The proportion of ownership interest and voting rights in a subsidiary attributable to the entity Proportion Of Ownership Interest And Voting Rights In Subsidiary Ownership and votes (Percentage) Disclosure of disaggregation of revenue from contracts with customers [table] The axis of a table defines the relationship between the domain members or categories in the table and the line items or concepts that complete the table. Types of revenues [axis] This member stands for This member stands for all types of revenues from customers. It also represents the standard value for the 'Types of revenues' axis if no other member is used. Types of revenues [member] This member stands for revenue form royalties. Royalties This member stands for reimbursement income. Reimbursement revenue This member stands for revenue from milestone payments. Milestone revenue This member stands for revenue from license fees. License revenue This member stands for collaboration revenue. Collaboration revenue Information by collaborative arrangement and arrangement other than collaborative applicable to revenue-generating activity or operations. Ifrs Collaborative Arrangement and Arrangement Other Than Collaborative [Axis] Collaborative arrangement and arrangement other than collaborative applicable to revenue-generating activity or operations. Ifrs Collaborative Arrangement and Arrangement Other Than Collaborative [Domain] This member stands for collaborative arrangement with Janssen (Darzalex/Daratumumab & DuoBody). Janssen This member stands for collaboration arrangement with Abbvie. AbbVie This member stands for collaboration arrangement with Roche. Roche This member stands for collaborative arrangement with Novartis (Arzaerra/Ofatumumab). Agreements With Novartis [Member] Novartis Novartis (Arzaerra/Ofatumumab) This member stands for collaboration arrangements with BioNTech. BioNTech This member stands for collaboration arrangement with Seagen. Seagen This member stands for collaborative arrangement with other collaboration partners. Other partners Information by royalties by product. ifrs Royalties by Product [Axis] Information by royalties by product. ifrs Royalties by Product [Domain] This member stands for DARZALEX. DARZALEX [Member] DARZALEX This member stands for TEPEZZA. TEPEZZA [Member] TEPEZZA This member stands for Kesimpta. Kesimpta [Member] Kesimpta This member stands for other royalty product. Other Royalty Product [Member] Other Disclosure of disaggregation of revenue from contracts with customers [line items] Revenue