Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, fair value	$ 91,557	$ 208,614
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	143,122	53,524
Short-term investments, fair value	91,557	208,614
Financial assets, fair value	234,679	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	143,122	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	4,500	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	25,913	41,259
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	16,036	59,971
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	45,108	92,508
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	143,122	39,524
Financial assets, fair value	143,122	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	143,122	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	91,557	208,614
Financial assets, fair value	91,557	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	4,500	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	25,913	41,259
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	16,036	59,971
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	$ 45,108	$ 92,508