v3.8.0.1
FAIR VALUE DISCLOSURE (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents $ 15,908 $ 25,244
Total cash equivalents and short-term investments, Amortized Cost 64,981 67,683
Total cash equivalents and short-term investments, Gross Unrealized Gain (Loss) (9) (31)
Total cash equivalents and short-term investments, Fair Value 64,972 67,652
Short-term Investments 49,064 42,408
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents, Amortized Cost 9,911 25,244
Cash equivalents 9,911 25,244
Level 1 | Money market funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents, Amortized Cost 9,911 25,244
Cash equivalents 9,911 25,244
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 5,997 0
Short-term investments 55,061 42,408
Securities, Amortized cost 55,070 42,439
Securities, Gross Unrealized Gain (Loss) (9) (31)
Short-term Investments 49,064 42,408
Level 2 | Commercial Paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0  
Level 2 | U.S. treasuries    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 5,997  
Level 2 | U.S. treasuries    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments 29,969 22,497
Securities, Amortized cost 29,974 22,516
Securities, Gross Unrealized Gain (Loss) (5) (19)
Short-term Investments 23,972 22,497
Level 2 | Corporate securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments 11,147 7,341
Securities, Amortized cost 11,151 7,353
Securities, Gross Unrealized Gain (Loss) (4) (12)
Short-term Investments 11,147 7,341
Level 2 | Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments 13,945 12,570
Securities, Amortized cost 13,945 12,570
Securities, Gross Unrealized Gain (Loss) 0 0
Short-term Investments $ 13,945 $ 12,570