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Summary of Significant Accounting Policies - Summary of Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis $ 76,343 $ 91,473 $ 108,028
Cash      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis 17    
Money Market Funds | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis 61,215 33,774 6,804
U.S. Treasury Securities | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis     238
U.S. Treasury Securities | Marketable Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis 15,111 57,699 100,986
Active Markets (Level 1)      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis 76,343 91,473 108,028
Active Markets (Level 1) | Cash      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis 17    
Active Markets (Level 1) | Money Market Funds | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis 61,215 33,774 6,804
Active Markets (Level 1) | U.S. Treasury Securities | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis     238
Active Markets (Level 1) | U.S. Treasury Securities | Marketable Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Assets measured at fair value on a recurring basis $ 15,111 $ 57,699 $ 100,986