Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2017

Accounting Policies [Abstract]

Percentage of Revenue from Significant Collaboration Customers

Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows:

	Three Months Ended June 30,						Six Months Ended June 30,
	2017			2016			2017			2016
Daiichi Sankyo, Inc.		53	%		31	%		47	%		37	%
Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		14	%		19	%		15	%		33	%
Bristol-Myers Squibb Company and Pfizer Inc.		27	%		41	%		31	%		24	%