The amount of development regulatory and commercial milestone payments to be made by the company under the agreement.

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

The amount of collaboration agreements, development regulatory and commercial milestone payment.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The amount of aggregate milestone payment received and receivable under an collaboration agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

The amount of applicable threshold net sale for calculation of tiered royalty percentage under the agreement.

+ References

No definition available.

+ Details

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- Definition

The percentage of royalties of worldwide net sales ofatumumab for the treatment of cancer under the agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the cost and profit sharing ratio.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of milestone payment receivable under an collaboration agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of milestone payment received under an collaboration agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage of royalties of worldwide net sales ofatumumab for the treatment of non-cancer under the agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of cost reimbursement from another partner if one partner bears certain costs under the arrangement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Term from first sale of the product after which obligation to pay royalties under the agreement will expire.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of tiered royalty under the collaboration agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of upfront fee payment made under an collaboration agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of upfront fee payable under an collaboration agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of additional proprietary targets of license.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of proprietary targets of license.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The period for which the entity has the option to obtain commercial license.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of options to obtain commercial license.

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

+ References

No definition available.

+ Details

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Namespace Prefix:	gmab_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of investments accounted for using the equity method. The equity method is a method of accounting whereby the investment is initially recognised at cost and adjusted thereafter for the post-acquisition change in the investor's share of net assets of the investee. The investor's profit or loss includes its share of the profit or loss of the investee. The investor's other comprehensive income includes its share of the other comprehensive income of the investee. [Refer: At cost [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2019-01-01
-Paragraph 24
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-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_24_a&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph B16
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_B16&doctype=Appendix&subtype=B
-URIDate 2019-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 54
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_54_e&doctype=Standard
-URIDate 2019-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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- Details

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OTHER DISCLOSURES - Collaborations and Technology Licenses (Details) € in Millions, kr in Millions, $ in Millions		1 Months Ended		3 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($)	Jul. 31, 2018 USD ($) property	Aug. 31, 2012	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) Option	Dec. 31, 2019 EUR (€)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 DKK (kr)	Dec. 19, 2019 DKK (kr)	Jul. 31, 2018 USD ($)	Jul. 31, 2018 item
Collaborations and Technology Licenses
Investments accounted for using equity method \| kr								kr 149
Janssen (Darzalex/Daratumumab & DuoBody)
Collaborations and Technology Licenses
Tiered royalty percentage	18.00%			20.00%
Royalty obligation expiration term after first sale of product					13 years
Applicable threshold net sale for calculating royalty percentage	$ 2.0			$ 3.0
Total milestone payment							$ 1,015.0
Milestone payments received					$ 835.0
Novartis (Arzaerra/Ofatumumab)
Collaborations and Technology Licenses
Royalty percentage for cancer treatment					20.00%
Royalty percentage for non-cancer treatment					10.00%
Seattle Genetics (Tisotumab vedotin)
Collaborations and Technology Licenses
Cost and profit sharing ratio					50
Cost reimbursement percentage					50.00%
CureVac
Collaborations and Technology Licenses
Upfront fee payable							10.0
Investments accounted for using equity method						€ 20		kr 149	kr 149
Collaborative arrangement, Development, Regulatory and commercial milestone payment							280.0
Options to obtain commercial licenses \| Option					3
Option exercisable period					5 years
Immatics
Collaborations and Technology Licenses
Development regulatory and commercial milestone payments to be made										$ 550.0
Collaborative arrangement, Development, Regulatory and commercial milestone payment										$ 550.0
Number of proprietary targets of license		3									3
Number of additional proprietary targets of license \| item											2
Upfront fee paid		$ 54.0
Minimum
Collaborations and Technology Licenses
Collaborative arrangement, Development, Regulatory and commercial milestone payment							275.0
Minimum \| Janssen (Darzalex/Daratumumab & DuoBody)
Collaborations and Technology Licenses
Tiered royalty percentage			12.00%
Minimum \| CureVac
Collaborations and Technology Licenses
Collaborative arrangement, Development, Regulatory and commercial milestone payment							275.0
Maximum
Collaborations and Technology Licenses
Collaborative arrangement, Development, Regulatory and commercial milestone payment							368.0
Maximum \| Janssen (Darzalex/Daratumumab & DuoBody)
Collaborations and Technology Licenses
Tiered royalty percentage			20.00%
Milestone payments receivable							180.0
Maximum \| CureVac
Collaborations and Technology Licenses
Collaborative arrangement, Development, Regulatory and commercial milestone payment							$ 368.0