Investments - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 504,305	$ 368,146
Gross unrealized gains	265	375
Gross unrealized losses	(26)	(6)
Estimated fair value	504,544	368,515
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized cost	130,814	160,065
Gross unrealized gains	160	233
Gross unrealized losses	(4)	(1)
Estimated fair value	$ 130,970	$ 160,297
Corporate debt securities \| Maximum
Debt Securities, Available-for-sale [Line Items]
Maturity	2 years	2 years
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 240,725	$ 120,862
Gross unrealized gains	58	74
Gross unrealized losses	(18)	0
Estimated fair value	$ 240,765	$ 120,936
Commercial paper \| Maximum
Debt Securities, Available-for-sale [Line Items]
Maturity	1 year	1 year
U.S. Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 83,227	$ 50,745
Gross unrealized gains	37	41
Gross unrealized losses	(1)	(4)
Estimated fair value	$ 83,263	$ 50,782
U.S. Agency bonds \| Maximum
Debt Securities, Available-for-sale [Line Items]
Maturity	2 years	2 years
U.S. Treasury bills
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 49,539	$ 36,474
Gross unrealized gains	10	27
Gross unrealized losses	(3)	(1)
Estimated fair value	$ 49,546	$ 36,500
U.S. Treasury bills \| Maximum
Debt Securities, Available-for-sale [Line Items]
Maturity	2 years	2 years

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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Amortized cost 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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