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Basis of Presentation - Activities of the subsidiary (Details) - Parent Company [Member] | 12 Months Ended
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Dec. 31, 2022 | Dec. 31, 2021
Genmab B.V. |  |
Activities of the subsidiary |  |
Ownership and votes (Percentage) | 100.00% | 100.00%
Genmab Holding B.V. |  |
Activities of the subsidiary |  |
Ownership and votes (Percentage) | 100.00% | 100.00%
Genmab US, Inc. |  |
Activities of the subsidiary |  |
Ownership and votes (Percentage) | 100.00% | 100.00%
Genmab K.K. |  |
Activities of the subsidiary |  |
Ownership and votes (Percentage) | 100.00% | 100.00%

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- Definition The proportion of ownership interest and voting rights in a subsidiary attributable to the entity + References No definition available. + Details
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Namespace Prefix: | gmab_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table. + References No definition available. + Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
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- Details
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Namespace Prefix: |
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- Details
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- Details
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