Initial fee received from collaboration or license agreement.

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Total potential clinical milestone payments company could earn under agreement.

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Total potential regulatory milestones company could earn under agreement

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Total potential sales milestones company could earn under agreement

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Proceeds From Research And Development Services

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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.

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Cash received on stock transaction after deduction of issuance costs.

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

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Collaboration and Other Agreements - Janssen Biotech, Inc. (Details) - Janssen Biotech, Inc. - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	May 31, 2016	Dec. 31, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Janssen MGD011 Agreement
Collaboration and Other Agreements [Line Items]
Sale of common stock (in shares)		1,923,077
Proceeds of stock sale		$ 75,000,000
Non-refundable upfront payment		$ 50,000,000
Janssen MGD015 Agreement
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 75,000,000
Revenue recognized under agreement			$ 200,000	$ 0	$ 500,000	$ 75,000,000
Janssen MGD015 Agreement \| Maximum
Collaboration and Other Agreements [Line Items]
Potential clinical milestone payments			100,000,000.0		100,000,000.0
Potential regulatory milestone payments under agreement			265,000,000.0		265,000,000.0
Potential sales milestone payments under agreement			$ 300,000,000.0		$ 300,000,000.0