Net realized and unrealized gains - Additional Information (Details) $ in Millions	3 Months Ended
Mar. 31, 2022 USD ($)
Investments, Debt and Equity Securities [Abstract]
Gain on sale of title plant copy	$ 1.0

Amount of gain (loss) on sale or disposal of intangible assets.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Name:	us-gaap_GainLossOnDispositionOfIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration