The Company and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2012	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company's incorporation date			Aug. 10, 1999
Commencement date of operations			Jun. 30, 2002
Change of entity name date			Apr. 19, 2005
Net loss	$ 16,805	$ 13,302	$ 32,207	$ 34,728	$ 32,207
Net cash used in operating activities			25,512	$ 33,260
Working capital surplus	127,100		127,100
Accumulated deficit	(291,004)		(291,004)			$ (258,797)
Cash, cash equivalents, and investments	$ 149,400		$ 149,400
Cash and cash equivalents, and investments, expected funding term for operating plan			12 months