Short-term Investments - Summary of Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 9,253	$ 119,675
Gross Unrealized Gains	7	0
Gross Unrealized Losses	0	(61)
Aggregate Fair Value	9,260	119,614
United States government debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,989	119,401
Gross Unrealized Gains	7	0
Gross Unrealized Losses	0	(61)
Aggregate Fair Value	8,996	119,340
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	264	274
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Aggregate Fair Value	$ 264	$ 274

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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