Summary of significant accounting policies - Risks (Details)	12 Months Ended
Dec. 31, 2023 USD ($)
Concentration of Credit Risk and Off-balance Sheet Risk
Financial instruments with off-balance sheet risk	$ 0

Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-21

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration