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Available-for-Sale Investments - Summary of Available-for-Sale Securities Held (Detail) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Amortized cost $ 94,741 $ 100,777
Gross unrealized gains 104 116
Gross unrealized losses (49) (4)
Fair Value 94,796 100,889
Commercial paper    
Schedule of Available-for-sale Securities [Line Items]    
Amortized cost 16,356 20,484
Gross unrealized gains 48 18
Gross unrealized losses   (1)
Fair Value 16,404 20,501
Corporate debt securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized cost 70,882 71,288
Gross unrealized gains 45 96
Gross unrealized losses (49) (1)
Fair Value 70,878 71,383
U.S. government agency securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized cost 7,503 9,005
Gross unrealized gains 11 2
Gross unrealized losses   (2)
Fair Value $ 7,514 $ 9,005