XML 83 R26.htm IDEA: XBRL DOCUMENT v2.4.0.8

Organization and Nature of Operations - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013 Segment
Organization And Nature Of Business [Line Items]
MacroGenics incorporated date	Aug. 14, 2000
Number of operating segments	1

X

- Definition

Date when an entity was incorporated

+ References

No definition available.

+ Details

Name:	dei_EntityIncorporationDateOfIncorporation
Namespace Prefix:	dei_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	mgnx_OrganizationAndNatureOfBusinessLineItems
Namespace Prefix:	mgnx_
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