Aggregate potential clinical milestone payments available to be earned under collaboration agreement.

No definition available.

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- Definition

Aggregate potential regulatory milestone payments available to be earned under a collaboration arrangement.

+ References

No definition available.

+ Details

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- Definition

Aggregate potential sales milestone payments available to be earned under collaboration agreement.

+ References

No definition available.

+ Details

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- Definition

Initial fee received from collaboration or license agreement.

+ References

No definition available.

+ Details

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- Definition

Amount by which purchase price exceeds fair value for common stock purchased by collaborator.

+ References

No definition available.

+ Details

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- Details

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- Definition

Revenue earned during the period relating to consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(e))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

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- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

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- Details

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Collaboration and License Agreements, Janssen Biotech, Inc. (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended			3 Months Ended	12 Months Ended
	May 31, 2014	Jan. 31, 2015	Dec. 31, 2014	Mar. 31, 2015	Dec. 31, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable upfront payment	$ 15.0mgnx_NonRefundableUpfrontFees
Janssen Biotech, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Sale of common stock (in shares)			1,923,077
Sale of common stock (in dollars per share)			$ 39.00		$ 39.00
Proceeds of stock sale					75.0
Additional Potential Clinical Milestone Payments Under Agreement				205.0
Additional Potential Regulatory Milestone Payments Under Agreement				220.0
Additional Potential Sales Milestone Payments Under Agreement				150.0
Premium received on stock purchase				12.3
Recognized revenue under agreement				62.3
Non-refundable upfront payment		$ 50.0