Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Line Items]
Cash	$ 26,847	$ 23,887
Cash equivalents:		143,029
Total cash and cash equivalents	86,317	166,916
Marketable securities, amortized cost	348,828	338,004
Marketable securities, gross unrealized gains	79	190
Marketable securities, gross unrealized losses	(2)	(1)
Marketable securities, estimated fair value	348,905	338,193
Total cash, cash equivalents and marketable securities, amortized cost	435,145	504,920
Total cash, cash equivalents and marketable securities	435,222	505,109
U.S. Treasuries
Cash and Cash Equivalents [Line Items]
Marketable securities, amortized cost	26,924	43,050
Marketable securities, gross unrealized gains	6	1
Marketable securities, gross unrealized losses	0	(1)
Marketable securities, estimated fair value	26,930	43,050
Money market funds
Cash and Cash Equivalents [Line Items]
Cash equivalents:	38,974	80,986
Certificate of deposits
Cash and Cash Equivalents [Line Items]
Cash equivalents:	1,500	1,000
Marketable securities, amortized cost	55,283	44,480
Marketable securities, gross unrealized gains	0	0
Marketable securities, gross unrealized losses	0	0
Marketable securities, estimated fair value	55,283	44,480
Commercial paper
Cash and Cash Equivalents [Line Items]
Cash equivalents:	18,996	61,043
Marketable securities, amortized cost	233,419	210,986
Marketable securities, gross unrealized gains	0	0
Marketable securities, gross unrealized losses	0	0
Marketable securities, estimated fair value	233,419	210,986
Corporate debt securities
Cash and Cash Equivalents [Line Items]
Marketable securities, amortized cost	27,002	33,288
Marketable securities, gross unrealized gains	59	172
Marketable securities, gross unrealized losses	(2)	0
Marketable securities, estimated fair value	27,059	33,460
U.S. Government-sponsored enterprises debt securities
Cash and Cash Equivalents [Line Items]
Marketable securities, amortized cost	6,200	6,200
Marketable securities, gross unrealized gains	14	17
Marketable securities, gross unrealized losses	0	0
Marketable securities, estimated fair value	$ 6,214	$ 6,217

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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