Name:	us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
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Data Type:	xbrli:stringItemType
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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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Data Type:	xbrli:monetaryItemType
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Represents the number of service agreements under arrangement other than collaborative.

No definition available.

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Data Type:	xbrli:integerItemType
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Represents the research service period under arrangement other than collaborative.

No definition available.

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Number of individuals.

No definition available.

Name:	ymab_NumberOfIndividuals
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Name:	us-gaap_TypeOfArrangementAxis=ymab_Cb33SponsoredResearchAgreementMember
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Name:	srt_TitleOfIndividualAxis=ymab_ResearchersEmployeesOfMskMember
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Name:	us-gaap_TypeOfArrangementAxis=ymab_MasterDataServicesAgreementMember
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