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401(k) Plan - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]      
Defined contribution plan, matching percentage 4.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent    
Defined contribution plan, matching amount $ 197us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount $ 91us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount $ 49us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount