Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities (Detail)

v3.21.1
Financial Instruments - Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]    
Total Fair Value $ 433,837 $ 499,345
Fair Value, Measurements, Recurring    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 433,676 499,049
Total Unrealized Gain 195 311
Total Unrealized Loss (34) (15)
Total Fair Value 433,837 499,345
Fair Value, Measurements, Recurring | Money Market Funds | Level 1    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 138,100 168,343
Total Unrealized Gain 0 0
Total Unrealized Loss 0 0
Total Fair Value 138,100 168,343
Fair Value, Measurements, Recurring | U.S. Treasury Obligations | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 176,010 230,239
Total Unrealized Gain 72 113
Total Unrealized Loss 0 (6)
Total Fair Value 176,082 230,346
Fair Value, Measurements, Recurring | Government Agency Obligations | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 25,218 22,537
Total Unrealized Gain 15 22
Total Unrealized Loss (6) (3)
Total Fair Value 25,227 22,556
Fair Value, Measurements, Recurring | Corporate Debt Obligations | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 61,259 50,080
Total Unrealized Gain 100 166
Total Unrealized Loss (20) (1)
Total Fair Value 61,339 50,245
Fair Value, Measurements, Recurring | Commercial Paper | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 22,242 17,990
Total Unrealized Gain 0 0
Total Unrealized Loss 0 0
Total Fair Value 22,242 17,990
Fair Value, Measurements, Recurring | Asset-Backed Securities | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 10,847 9,860
Total Unrealized Gain 8 10
Total Unrealized Loss (8) (5)
Total Fair Value 10,847 9,865
Fair Value, Measurements, Recurring | Amounts Classified As Cash Equivalents    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost (149,773) (199,090)
Total Unrealized Gain 0 0
Total Unrealized Loss 0 0
Total Fair Value (149,773) (199,090)
Fair Value, Measurements, Recurring | Amounts Classified As Short-Term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 283,903 299,959
Total Unrealized Gain 195 311
Total Unrealized Loss (34) (15)
Total Fair Value $ 284,064 $ 300,255