Cash and Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents
Realized Investment Gains (Losses)	$ 0
Available-for-sale Securities, Amortized Cost Basis	26,018
Available-for-sale Securities, Gross Unrealized Gain Accumulated in Investments	5
Available-for-sale Securities, Gross Unrealized Losses	(11)
Available-for-sale Securities, Current	26,012
Cash
Cash and Cash Equivalents
Available-for-sale Securities, Amortized Cost Basis	126,263	$ 36,112
Available-for-sale Securities, Gross Unrealized Gain Accumulated in Investments	0	0
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Current	126,263	36,112
US Treasury Securities
Cash and Cash Equivalents
Available-for-sale Securities, Amortized Cost Basis		235,463
Available-for-sale Securities, Gross Unrealized Gain Accumulated in Investments		94
Available-for-sale Securities, Gross Unrealized Losses		(10)
Available-for-sale Securities, Current		235,547
Short-term Investments
Cash and Cash Equivalents
Available-for-sale Securities, Amortized Cost Basis	26,018	235,463
Available-for-sale Securities, Gross Unrealized Gain Accumulated in Investments	5	94
Available-for-sale Securities, Gross Unrealized Losses	(11)	(10)
Available-for-sale Securities, Current	26,012	235,547
Cash and Cash Equivalents and Investments
Cash and Cash Equivalents
Available-for-sale Securities, Amortized Cost Basis	152,281	271,575
Available-for-sale Securities, Gross Unrealized Gain Accumulated in Investments	5	94
Available-for-sale Securities, Gross Unrealized Losses	(11)	(10)
Available-for-sale Securities, Current	$ 152,275	$ 271,659

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

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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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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Amount of realized gain (loss) on investment.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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