Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Investments (Details)

v3.20.1
Fair Value of Investments (Details) - Recurring - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets $ 75,873 $ 87,597
Money market funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 28,728 26,812
U.S. government securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 4,579 4,544
Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 14,833 17,754
Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 22,629 24,679
Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 5,104 13,808
Quoted Prices in Active Markets for Identical Assets (Level 1)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 33,307 31,356
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 28,728 26,812
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. government securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 4,579 4,544
Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 42,566 56,241
Significant Other Observable Inputs (Level 2) | Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 14,833 17,754
Significant Other Observable Inputs (Level 2) | Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 22,629 24,679
Significant Other Observable Inputs (Level 2) | Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets $ 5,104 $ 13,808