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Collaboration and Other Agreements, Janssen Biotech, Inc. (Details) - Janssen Biotech Inc. - USD ($) $ / shares in Units, $ in Millions	1 Months Ended			12 Months Ended
	Jul. 31, 2016	Jan. 31, 2015	Dec. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2015
Janssen MGD011 Agreement
Collaboration and Other Agreements [Line Items]
Sale of common stock (in shares)			1,923,077
Proceeds of stock sale		$ 75.0	$ 75.0
Non-refundable upfront payment						$ 50.0
Sale of common stock (in dollars per share)		$ 39.00
Premium received on stock purchase		$ 12.3
Total consideration		125.0
Amount allocated to equity		62.7
Amount allocated to license and R&D		$ 62.3
Clinical milestone earned during period							$ 10.0
Recognized revenue under agreement				$ 0.0	$ 2.0	$ 72.3
Janssen MGD015 Agreement
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 75.0				75.0
Recognized revenue under agreement				$ 0.6	$ 75.8

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+ 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=63488584&loc=d3e20235-122688

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