Short-term Investments - Summary of Short-term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	$ 252,353	$ 318,989
Available-for-sale securities, gross unrealized gains	932	85
Available-for-sale securities, gross unrealized losses	(224)
Available-for-sale securities	253,061	319,074
U.S. Treasury Bills and Government Agency Obligations
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	100,499	140,567
Available-for-sale securities, gross unrealized gains	932	59
Available-for-sale securities	101,431	140,626
U.S. Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	70,077	80,159
Available-for-sale securities, gross unrealized gains		11
Available-for-sale securities, gross unrealized losses	(139)
Available-for-sale securities	69,938	80,170
Foreign Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	25,578	23,188
Available-for-sale securities, gross unrealized gains		15
Available-for-sale securities, gross unrealized losses	(85)
Available-for-sale securities	25,493	23,203
U.S. Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	25,873	32,801
Available-for-sale securities	25,873	32,801
Foreign Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	30,326	42,274
Available-for-sale securities	$ 30,326	$ 42,274

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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