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Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
Jun. 30, 2021
Dec. 31, 2020
Contingent Consideration Obligations [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Liabilities, fair value on recurring basis $ (46,000) $ (227,000)
Failed Auction Security [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Estimated Fair Value 2,561,000 2,517,000
Failed Auction Security [Member] | Other Long-term Investments [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Estimated Fair Value 2,561,000 2,517,000
US Treasury Obligations [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Cash equivalents 70,469,000 19,998,000
Estimated Fair Value 70,469,000 70,164,000
US Treasury Obligations [Member] | Short-term Investments [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Estimated Fair Value   50,166,000
Money Market Funds [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Cash equivalents 68,978,000 69,493,000
Recurring [Member] | Quoted Prices in Active Markets (Level 1) [Member] | US Treasury Obligations [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Cash equivalents 70,469,000 19,998,000
Recurring [Member] | Quoted Prices in Active Markets (Level 1) [Member] | US Treasury Obligations [Member] | Short-term Investments [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Estimated Fair Value   50,166,000
Recurring [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Money Market Funds [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Cash equivalents 68,978,000 69,493,000
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Contingent Consideration Obligations [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Liabilities, fair value on recurring basis (46,000) (227,000)
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Failed Auction Security [Member] | Other Long-term Investments [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Estimated Fair Value $ 2,561,000 $ 2,517,000