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Marketable Securities and Fair Value Measurements - Estimate of Fair Value of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 74,753	$ 83,929
Gross Unrealized Gains	106	252
Gross Unrealized Losses	(8)	(1)
Fair Value	74,851	84,180
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,150	10,548
Gross Unrealized Gains	0	10
Gross Unrealized Losses	0	0
Fair Value	2,150	10,558
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	45,070	51,745
Gross Unrealized Gains	83	207
Gross Unrealized Losses	(8)	(1)
Fair Value	45,145	51,951
U.S. Treasury and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,493	9,222
Gross Unrealized Gains	12	3
Gross Unrealized Losses	0	0
Fair Value	9,505	9,225
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	12,136	500
Gross Unrealized Gains	0
Gross Unrealized Losses	0	0
Fair Value	12,136	500
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,904	11,914
Gross Unrealized Gains	11	32
Gross Unrealized Losses	0	0
Fair Value	$ 5,915	$ 11,946

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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