Components of Fixed Assets (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fixed Assets [Line Items]
Laboratory equipment	$ 7,673	$ 7,628
Furniture and office equipment	1,619	1,619
Software and computers	5,357	4,763
Leasehold improvements	4,510	4,502
Construction in process		197
Total	19,159	18,709
Less: accumulated depreciation	(14,020)	(13,380)
Property, plant and equipment, Net	$ 5,139	$ 5,329