Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2014

Revenue Accounted for 10% or More of Total Revenues

Customers whose collaborative research and development revenue accounted for 10% or more of total revenues were as follows:

	Three Months Ended June 30,						Six Months Ended June 30,
	2014			2013			2014			2013
Bristol-Myers Squibb Company and Pfizer Inc.		21	%		43	%		20	%		54	%
Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		49	%		51	%		44	%		43	%
Daiichi Sankyo, Inc.		27	%		—			34	%		—