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Available-for-Sale Securities - Summary Estimated Fair Value and Amortized Cost of Available-for-Sale Securities by Contractual Maturity (Detail) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]    
Due in one year or less, amortized cost $ 401 $ 7,480
Amortized Cost 401 7,480
Due in one year or less, fair value 400 7,481
Total available-for-sale securities, fair value $ 400 $ 7,481