Annual report pursuant to Section 13 and 15(d)

Nature of Business and Basis of Presentation - Additional Information (Detail)

v2.4.1.9
Nature of Business and Basis of Presentation - Additional Information (Detail) (USD $)
Dec. 31, 2014
Dec. 31, 2013
Organization Consolidation And Presentation Of Financial Statements [Abstract]    
Accumulated deficit $ 159,958,000us-gaap_RetainedEarningsAccumulatedDeficit $ 133,689,000us-gaap_RetainedEarningsAccumulatedDeficit
Cash equivalents and short-term investments $ 47,100,000us-gaap_CashCashEquivalentsAndShortTermInvestments