Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		$ 208,614
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 177,753	53,524
Short-term investments, fair value		208,614
Financial assets, fair value		262,138
Fair Value, Measurements, Recurring | Money Market Mutual Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	177,753	39,524
Fair Value, Measurements, Recurring | Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value		14,000
Fair Value, Measurements, Recurring | Asset-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		14,876
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		41,259
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		92,508
Fair Value, Measurements, Recurring | U.S Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		59,971
Fair Value, Measurements, Recurring | Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	177,753	39,524
Financial assets, fair value		39,524
Fair Value, Measurements, Recurring | Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1) | Money Market Mutual Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 177,753	39,524
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value		14,000
Short-term investments, fair value		208,614
Financial assets, fair value		222,614
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value		14,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		14,876
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		41,259
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		92,508
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value		$ 59,971