Financial Instruments - Fair value hierarchy (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2022	Dec. 31, 2021
Reverse repurchase agreements \| Government Securities and Obligations \| Minimum
Financial Instruments
Percentage of investment amount to collateralized deposits value	102.00%
Recurring
Assets:
Total	$ 87,543	$ 40,853
Recurring \| Level 1
Assets:
Total	3,391	1,853
Recurring \| Level 2
Assets:
Total	84,152	39,000
Recurring \| Money market funds
Assets:
Cash equivalents	3,391	1,853
Recurring \| Money market funds \| Level 1
Assets:
Cash equivalents	3,391	1,853
Recurring \| Corporate debt securities
Assets:
Cash equivalents	1,000
Short-term investments	23,685
Recurring \| Corporate debt securities \| Level 2
Assets:
Cash equivalents	1,000
Short-term investments	23,685
Recurring \| Commercial paper
Assets:
Short-term investments	8,984
Recurring \| Commercial paper \| Level 2
Assets:
Short-term investments	8,984
Recurring \| Yankee securities
Assets:
Short-term investments	6,998
Recurring \| Yankee securities \| Level 2
Assets:
Short-term investments	6,998
Recurring \| U.S. agency bonds
Assets:
Short-term investments	2,985
Recurring \| U.S. agency bonds \| Level 2
Assets:
Short-term investments	2,985
Recurring \| Reverse repurchase agreements
Assets:
Cash equivalents	10,500
Short-term investments	30,000	39,000
Recurring \| Reverse repurchase agreements \| Level 2
Assets:
Cash equivalents	10,500
Short-term investments	$ 30,000	$ 39,000

The percentage of investment in reverse repurchase agreements which are collateralized by deposits.

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- Definition

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
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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- References

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- Definition

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.

+ References

No definition available.

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- Definition

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+ References

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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