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v3.25.1

LEASES - Additional Information (Details) | 3 Months Ended
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Mar. 31, 2025 USD ($)
Leasehold land |
Leases [Line Items] |
Lessee, lease terms | 50 years
Ongoing lease payments | $ 0
Bottom of Range |
Leases [Line Items] |
Lessee, lease terms | 3 years
Top of Range |
Leases [Line Items] |
Lessee, lease terms | 29 years

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- Definition Leases line items. + References No definition available. + Details
Name: | legn_LeasesLineItems
Namespace Prefix: | legn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Lessee leasing arrangements leases term. + References No definition available. + Details
Name: | legn_LesseeLeasingArrangementsLeasesTerm
Namespace Prefix: | legn_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Ongoing lease payments under the land lease. + References No definition available. + Details
Name: | legn_OngoingLeasePaymentsUnderTheLandLease
Namespace Prefix: | legn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=ifrs-full_LandMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |