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)

v3.20.1
Financial Instruments - Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Total Fair Value $ 213,127 $ 257,299
Fair Value, Measurements, Recurring    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 212,922 257,078
Total Unrealized Gain 421 233
Total Unrealized Loss (216) (12)
Total Fair Value 213,127 257,299
Fair Value, Measurements, Recurring | Money Market Funds | Level 1    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 42,382 63,554
Total Unrealized Gain 0 0
Total Unrealized Loss 0 0
Total Fair Value 42,382 63,554
Fair Value, Measurements, Recurring | U.S. Treasury Obligations | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 58,993 52,805
Total Unrealized Gain 318 46
Total Unrealized Loss 0 (1)
Total Fair Value 59,311 52,850
Fair Value, Measurements, Recurring | Government Agency Obligations | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 6,686 6,151
Total Unrealized Gain 9 1
Total Unrealized Loss (2) (1)
Total Fair Value 6,693 6,151
Fair Value, Measurements, Recurring | Corporate Debt Obligations | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 85,121 100,512
Total Unrealized Gain 92 180
Total Unrealized Loss (210) (10)
Total Fair Value 85,003 100,682
Fair Value, Measurements, Recurring | Commercial Paper | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 14,471 26,290
Total Unrealized Gain 0 0
Total Unrealized Loss 0 0
Total Fair Value 14,471 26,290
Fair Value, Measurements, Recurring | Asset-Backed Securities | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 5,269 7,266
Total Unrealized Gain 2 6
Total Unrealized Loss (4)  
Total Fair Value 5,267 7,272
Fair Value, Measurements, Recurring | Certificates of Deposit | Level 2    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost   500
Total Unrealized Gain   0
Total Unrealized Loss   0
Total Fair Value   500
Fair Value, Measurements, Recurring | Amounts Classified As Cash Equivalents    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost (68,689) (72,507)
Total Unrealized Gain (10) 0
Total Unrealized Loss 0 0
Total Fair Value (68,699) (72,507)
Fair Value, Measurements, Recurring | Amounts Classified As Short-Term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Total Amortized Cost 144,233 184,571
Total Unrealized Gain 411 233
Total Unrealized Loss (216) (12)
Total Fair Value $ 144,428 $ 184,792