XML 57 R29.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2014 Segment Assets | Dec. 31, 2013 Assets
Revenue, Major Customer [Line Items] |  |
Effective date of merger | Dec. 22, 2014 |
Number of operating segments | 1 us-gaap_NumberOfOperatingSegments |
Original maturity of financial instruments | 3 months | 3 months
Allowance recorded | $ 0 us-gaap_AllowanceForDoubtfulAccountsReceivable | $ 0 us-gaap_AllowanceForDoubtfulAccountsReceivable
Amounts classified as restricted cash | $ 300,000 us-gaap_RestrictedCashAndCashEquivalents | $ 405,000 us-gaap_RestrictedCashAndCashEquivalents
Number of impaired assets | 0 mgnx_NumberOfImpairedAssets | 0 mgnx_NumberOfImpairedAssets
Number of assets held-for-sale | 0 mgnx_NumberOfAssetsHeldForSale | 0 mgnx_NumberOfAssetsHeldForSale
Minimum [Member] | Sales Revenue, Net [Member] |  |
Revenue, Major Customer [Line Items] |  |
Percentage of all significant revenue earned | 10.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_SalesRevenueNetMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
Minimum [Member] | Accounts Receivable [Member] |  |
Revenue, Major Customer [Line Items] |  |
Percentage of all significant revenue earned | 10.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_AccountsReceivableMember / us-gaap_RangeAxis = us-gaap_MinimumMember |

X
- Definition Effective date of merger of subsidiary into parent. + References No definition available. + Details
Name: | mgnx_BusinessMergerEffectiveDate
Namespace Prefix: | mgnx_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Liquid investment maturity period to be classified as cash equivalent maximum. + References No definition available. + Details
Name: | mgnx_LiquidInvestmentMaturityPeriodToBeClassifiedAsCashEquivalentMaximum
Namespace Prefix: | mgnx_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of assets held for sale. + References No definition available. + Details
Name: | mgnx_NumberOfAssetsHeldForSale
Namespace Prefix: | mgnx_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of impaired assets. + References No definition available. + Details
Name: | mgnx_NumberOfImpairedAssets
Namespace Prefix: | mgnx_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 4 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5074-111524 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 210.5-02.4) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_AllowanceForDoubtfulAccountsReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13537-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13531-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References No definition available. + Details
Name: | us-gaap_NumberOfOperatingSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_RestrictedCashAndCashEquivalents
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |