Financial instruments and fair value measurements - Investments in fixed maturity securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financial instruments and fair value measurements
Amortized Cost	$ 249,136	$ 285,466
Gross Unrealized Gains	87	2
Gross Unrealized Losses	(1,271)	(2,390)
Fair Value	247,953	283,078
U.S. Treasury
Financial instruments and fair value measurements
Amortized Cost	65,807	87,798
Gross Unrealized Losses	(610)	(1,323)
Fair Value	65,197	86,475
Corporate bonds
Financial instruments and fair value measurements
Amortized Cost	183,329	197,668
Gross Unrealized Gains	87	2
Gross Unrealized Losses	(660)	(1,067)
Fair Value	$ 182,756	$ 196,603

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Section 50
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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