XML 31 R48.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Lease Exit Liability - Additional Information (Detail) (USD $) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jul. 16, 2008 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Restructuring Cost and Reserve [Line Items] |  |  |  |
Operating Lease | 2018 |  |  |
Onetime purchase payment under purchase agreement | $ 5,000,000 |  |  |
Additional amounts recorded |  | 0 | 0 | 0
Minimum [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Onetime payment paid under license of product | 8,000,000 |  |  |
Maximum [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Onetime payment paid under license of product | $ 12,000,000 |  |  |
Convertible Preferred Stock Series D [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Shares issued in connection with acquisition | 12,466,039 |  |  |

X
- Definition Contingent consideration recorded as incremental in process research and development expense. + References No definition available. + Details
Name: | mgnx_ContingentConsiderationRecordedAsIncrementalInProcessResearchAndDevelopmentExpense
Namespace Prefix: | mgnx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Lease expiration year. + References No definition available. + Details
Name: | mgnx_LeaseExpirationYear
Namespace Prefix: | mgnx_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition One-time milestone payment to be paid under agreement. + References No definition available. + Details
Name: | mgnx_OnetimeMilestonePaymentToBePaidUnderAgreement
Namespace Prefix: | mgnx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition One-time milestone payment to be paid under agreement upon specified level of sales of products. + References No definition available. + Details
Name: | mgnx_OnetimeMilestonePaymentToBePaidUnderAgreementUponSpecifiedLevelOfSalesOfProducts
Namespace Prefix: | mgnx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RestructuringCostAndReserveLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares of stock issued during the period pursuant to acquisitions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.28,29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesAcquisitions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration