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Available-for-Sale Marketable Securities in Unrealized Position (Detail) - USD ($)
Mar. 31, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Total, Unrealized Loss   $ 0
Corporate debt securities    
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 Months, Fair Value $ 55,318,000  
Less than 12 Months, Unrealized Loss 487,000  
Total, Fair Value 55,318,000  
Total, Unrealized Loss $ 487,000