Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investments
Debt Securities, available-for-sale, accrued interest	$ 400	$ 300
Fair value, measurements, recurring
Investments
Total assets at fair value	133,778	168,726
Fair value, measurements, recurring \| Corporate commercial paper, bonds and notes
Investments
Short-term investments:	75,870	38,884
Long-term investments:	23,964	14,564
Fair value, measurements, recurring \| Money market funds
Cash equivalents:
Cash equivalents	33,944	115,278
Fair value, measurements, recurring \| Quoted Prices in Active Markets (Level 1)
Investments
Total assets at fair value	33,944	115,278
Fair value, measurements, recurring \| Quoted Prices in Active Markets (Level 1) \| Corporate commercial paper, bonds and notes
Investments
Short-term investments:	0	0
Long-term investments:	0	0
Fair value, measurements, recurring \| Quoted Prices in Active Markets (Level 1) \| Money market funds
Cash equivalents:
Cash equivalents	33,944	115,278
Fair value, measurements, recurring \| Other Observable Inputs (Level 2)
Investments
Total assets at fair value	99,834	53,448
Fair value, measurements, recurring \| Other Observable Inputs (Level 2) \| Corporate commercial paper, bonds and notes
Investments
Short-term investments:	75,870	38,884
Long-term investments:	23,964	14,564
Fair value, measurements, recurring \| Other Observable Inputs (Level 2) \| Money market funds
Cash equivalents:
Cash equivalents	0	0
Fair value, measurements, recurring \| Unobservable Inputs (Level 3)
Investments
Total assets at fair value	0	0
Fair value, measurements, recurring \| Unobservable Inputs (Level 3) \| Corporate commercial paper, bonds and notes
Investments
Short-term investments:	0	0
Long-term investments:	0	0
Fair value, measurements, recurring \| Unobservable Inputs (Level 3) \| Money market funds
Cash equivalents:
Cash equivalents	$ 0	$ 0

Debt Securities, Available-for-Sale, Accrued Interest

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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-Name Accounting Standards Codification
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-Section 45
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as noncurrent.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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