Company Overview - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	[1]
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Date of incorporation	Feb. 10, 1998
Cash, cash equivalents and marketable securities	$ 40,000
Accumulated deficit	$ (569,459)	$ (559,373)
Maturity limits period	24 months
Dollars weighted average maturity limit period	12 months

[1] The condensed consolidated balance sheet as of December 31, 2015 has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015.