Strategic Alliances and Collaborations (Revenue from Strategic Alliances) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue from External Customer [Line Items]
Total revenues	$ 18	$ 483	$ 36	$ 972
Strategic Alliances and Collaborations
Revenue from External Customer [Line Items]
Total revenues	18	483	36	972
Strategic Alliances and Collaborations \| Sanofi
Revenue from External Customer [Line Items]
Total revenues	18	18	36	36
Strategic Alliances and Collaborations \| AstraZeneca
Revenue from External Customer [Line Items]
Total revenues	$ 0	$ 465	$ 0	$ 936

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration