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Cash Equivalents and Investments - Schedule of Investments (Detail) - USD ($)
$ in Thousands
Jun. 30, 2020
Dec. 31, 2019
Available-for-sale [Line Items]    
Available-for-sale Securities $ 90,642 $ 74,510
Corporate Securities [Member]    
Available-for-sale [Line Items]    
Available-for-sale Securities 55,677 32,962
Municipal Debt Securities [Member]    
Available-for-sale [Line Items]    
Available-for-sale Securities 20,831 29,066
Federal Home Loan Securities [Member]    
Available-for-sale [Line Items]    
Available-for-sale Securities 8,537 8,013
Certificates of Deposit [Member]    
Available-for-sale [Line Items]    
Available-for-sale Securities $ 5,597 $ 4,469