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Marketable Securities - Fair Value of Available for Sale Marketable Securities (Detail) - Level 2 [Member] - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities, Adjusted Cost $ 34,686 $ 41,326
Available for sale securities, Unrealized Gains   7
Available for sale securities, Unrealized Losses (101) (5)
Available for sale securities, Fair Value 34,585 41,328
Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities, Adjusted Cost 34,686 37,325
Available for sale securities, Unrealized Gains   7
Available for sale securities, Unrealized Losses (101) (5)
Available for sale securities, Fair Value $ 34,585 37,327
Government-Sponsored Enterprises Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities, Adjusted Cost   4,001
Available for sale securities, Fair Value   $ 4,001