XML 42 R31.htm IDEA: XBRL DOCUMENT v3.19.2
Fair Value of Financial Instruments - Summary of Fair Value Hierarchy for Financial Assets (Detail) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total $ 49,455  
Fair Value, Measurements, Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 49,455 $ 41,921
Fair Value, Measurements, Recurring [Member] | Money Market Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 6,547 1,472
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 39,262 28,343
Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 2,002  
Fair Value, Measurements, Recurring [Member] | Corporate Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 1,644 12,106
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 6,547 1,472
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 6,547 1,472
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0 0
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0  
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0 0
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 42,908 40,449
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0 0
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 39,262 28,343
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 2,002  
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 1,644 12,106
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0 0
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0 0
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0 0
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total 0  
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Notes [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total $ 0 $ 0