Name:	us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the additional sales based milestone payments potentially due under arrangement other than collaborative for each of the constructs previously generated using the technology from specified agreement and sold for the company by a sublicensee.

No definition available.

Name:	ymab_ArrangementOtherThanCollaborativeAdditionalSalesBasedMilestonePaymentsDueOtherConstructs
Namespace Prefix:	ymab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the annual minimum royalties payable under arrangement other than collaborative.

No definition available.

Name:	ymab_ArrangementOtherThanCollaborativeAnnualMinimumRoyaltiesPayable
Namespace Prefix:	ymab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the annual minimum royalties payable from tenth anniversary under arrangement other than collaborative.

No definition available.

Name:	ymab_ArrangementOtherThanCollaborativeAnnualMinimumRoyaltiesPayableFromTenthAnniversary
Namespace Prefix:	ymab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the clinical milestone payments potentially due under arrangement other than collaborations.

No definition available.

Name:	ymab_ArrangementOtherThanCollaborativeClinicalMilestonePaymentsDue
Namespace Prefix:	ymab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the regulatory milestone payments potentially due under arrangement other than collaborative.

No definition available.

Name:	ymab_ArrangementOtherThanCollaborativeRegulatoryMilestonePaymentsDue
Namespace Prefix:	ymab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the sales based milestones payments potentially due under arrangement other than collaborative.

No definition available.

Name:	ymab_ArrangementOtherThanCollaborativeSalesBasedMilestonePaymentsDue
Namespace Prefix:	ymab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the upfront payment under arrangement other than collaborative.

No definition available.

Name:	ymab_ArrangementOtherThanCollaborativeUpfrontPayment
Namespace Prefix:	ymab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of new stock issued to the strategic partner during the period.

No definition available.