Financial Instruments - Fair value hierarchy (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 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	$ 85,666	$ 40,853
Recurring \| Level 1
Assets:
Total	10,144	1,853
Recurring \| Level 2
Assets:
Total	75,522	39,000
Recurring \| Money market funds
Assets:
Cash equivalents	8,145	1,853
Recurring \| Money market funds \| Level 1
Assets:
Cash equivalents	8,145	1,853
Recurring \| Corporate debt securities
Assets:
Cash equivalents	4,396
Short-term investments	17,121
Recurring \| Corporate debt securities \| Level 2
Assets:
Cash equivalents	4,396
Short-term investments	17,121
Recurring \| Commercial paper
Assets:
Cash equivalents	3,996
Short-term investments	5,980
Recurring \| Commercial paper \| Level 2
Assets:
Cash equivalents	3,996
Short-term investments	5,980
Recurring \| Yankee securities
Assets:
Short-term investments	4,029
Recurring \| Yankee securities \| Level 2
Assets:
Short-term investments	4,029
Recurring \| Treasury Bills
Assets:
Short-term investments	1,999
Recurring \| Treasury Bills \| Level 1
Assets:
Short-term investments	1,999
Recurring \| Reverse repurchase agreements
Assets:
Cash equivalents	3,000
Short-term investments	37,000	39,000
Recurring \| Reverse repurchase agreements \| Level 2
Assets:
Cash equivalents	3,000
Short-term investments	$ 37,000	$ 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 http://asc.fasb.org/extlink&oid=123874694&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 http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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