Investments in Marketable Securities - Schedule of Investments in Marketable Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investments in marketable securities:
Amortized Cost	$ 59,444	$ 46,732
Estimated Fair Value	156,969	227,311
Amortized Cost	211,017	269,817
Gross Unrealized Gain	7	79
Gross Unrealized Loss	(4)	(7)
Estimated Fair Value	211,020	269,889
Cash equivalents
Investments in marketable securities:
Amortized Cost	54,051	42,579
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	(1)
Estimated Fair Value	54,051	42,578
Cash equivalents \| Money market fund
Investments in marketable securities:
Amortized Cost	47,553	33,095
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	47,553	33,095
Cash equivalents \| U.S and foreign corporate debt securities
Investments in marketable securities:
Amortized Cost		5,000
Gross Unrealized Gain		0
Gross Unrealized Loss		(1)
Estimated Fair Value		4,999
Cash equivalents \| U.S. and foreign commercial paper
Investments in marketable securities:
Amortized Cost	6,498	4,484
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	6,498	4,484
Short-term investments
Investments in marketable securities:
Amortized Cost	156,966	227,238
Gross Unrealized Gain	7	79
Gross Unrealized Loss	(4)	(6)
Estimated Fair Value	156,969	227,311
Short-term investments \| U.S and foreign corporate debt securities
Investments in marketable securities:
Amortized Cost	16,939	72,452
Gross Unrealized Gain	3	38
Gross Unrealized Loss	(3)	(4)
Estimated Fair Value	16,939	72,486
Short-term investments \| Asset-backed securities
Investments in marketable securities:
Amortized Cost	12,674	34,008
Gross Unrealized Gain	2	17
Gross Unrealized Loss	(1)	0
Estimated Fair Value	12,675	34,025
Short-term investments \| U.S. treasury securities
Investments in marketable securities:
Amortized Cost	23,997	44,692
Gross Unrealized Gain	2	24
Gross Unrealized Loss	0	(2)
Estimated Fair Value	23,999	44,714
Short-term investments \| U.S. and foreign commercial paper
Investments in marketable securities:
Amortized Cost	103,356	76,086
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	$ 103,356	$ 76,086

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