Summary of significant accounting policies - Fair Value of Recurring Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Feb. 28, 2022	Dec. 31, 2021
Assets
Strategic investments	$ 15,000	$ 15,000	$ 10,000
Fair Value, Recurring \| Level 1
Assets
Strategic investments	0		0
Total assets, fair value	0		0
Liabilities
Cash settled stock appreciation rights	0		0
Total liabilities, fair value	0		0
Fair Value, Recurring \| Level 2
Assets
Strategic investments	0		0
Total assets, fair value	0		0
Liabilities
Cash settled stock appreciation rights	0		0
Total liabilities, fair value	0		0
Fair Value, Recurring \| Level 3
Assets
Strategic investments	15,000		10,000
Total assets, fair value	15,000		10,000
Liabilities
Cash settled stock appreciation rights	419		818
Total liabilities, fair value	$ 419		$ 818

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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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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI https://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740

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- Definition

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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