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Marketable Securities - Schedule of Fair Value and Amortized Cost of Company's Available-for-Sale Securities by Contractual Maturity (Detail) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]      
Due in one year or less, Amortized Cost $ 15,079 $ 57,650 $ 101,027
Total, Amortized Cost 15,079 57,650 101,027
Due in one year or less, Fair Value 15,111 57,699 100,986
Total, Fair Value $ 15,111 $ 57,699 $ 100,986