XML 69 R46.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Lease Exit Liability Lease Exit Liability - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2015 | Jul. 06, 2017 | May 31, 2016
Restructuring Cost and Reserve [Line Items] |  |  |  |
Future sublease payments to be received | $ 0.1 |  | $ 2.4 |
Reduction in research and development expense | $ 1.3 |  |  |
Reduction of research and development expense |  | $ 1.9 |  |
Raven Biotechnologies Inc. |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Future sublease payments to be received |  |  |  | $ 1.3

X
- Definition Amount of immaterial error correction made during period + References No definition available. + Details
Name: | mgnx_AmountOfImmaterialErrorCorrection
Namespace Prefix: | mgnx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Reduction In Research And Development Expense + References No definition available. + Details
Name: | mgnx_ReductionInResearchAndDevelopmentExpense
Namespace Prefix: | mgnx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Contractually required future rental payments receivable on noncancelable subleasing arrangements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
Name: | us-gaap_OperatingLeasesFutureMinimumPaymentsDueFutureMinimumSubleaseRentals
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_RestructuringCostAndReserveLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=mgnx_RavenBiotechnologiesIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |