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Available-for-sale Securities and Fair Value on Financial Instruments - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale securities in unrealized net loss position     $ 0
Credit losses recognized $ 0 $ 0  
Gross realized gains from the sale or maturity of available-for-sale investments   0  
Gross realized losses from the sale or maturity of available-for-sale investments 300,000 $ 0  
Maximum      
Schedule of Available-for-sale Securities [Line Items]      
Gross realized gains from the sale or maturity of available-for-sale investments $ 100,000