Fair value measurements - Changes in fair value of Level 3 measurements (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Changes in fair value measurement, assets [abstract]
Transfers out of Level 2 into Level 1 of fair value hierarchy, assets held at end of reporting period	$ 100	$ 800
Percentage increase in unobservable input (percent)	5.00%	5.00%
Percentage decrease in unobservable input (percent)		5.00%
Increase (decrease) in fair value measurement due to reasonably possible increase in unobservable input, recognised in profit or loss	$ 200	$ 300
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, recognised in profit or loss	200	300
Recurring fair value measurements \| Current investments \| Level 3
Changes in fair value measurement, assets [abstract]
Financial assets at beginning of period	1,532	2,155
Purchases and reclassifications	48	(44)
Sales	(37)	0
Net unrealized gains (losses) included in net income	(63)	(579)
Financial assets at end of period	1,480	1,532
Recurring fair value measurements \| Share purchase warrants \| Level 3
Changes in fair value measurement, assets [abstract]
Financial assets at beginning of period	47	135
Purchases and reclassifications	48	(44)
Sales	(37)	0
Net unrealized gains (losses) included in net income	(56)	(44)
Financial assets at end of period	2	47
Recurring fair value measurements \| Private holdings \| Level 3
Changes in fair value measurement, assets [abstract]
Financial assets at beginning of period	1,485	2,020
Purchases and reclassifications	0	0
Sales	0	0
Net unrealized gains (losses) included in net income	(7)	(535)
Financial assets at end of period	1,478	1,485
Recurring fair value measurements \| Total Other assets \| Level 3
Changes in fair value measurement, assets [abstract]
Financial assets at beginning of period	3,778	7,060
Purchases and reclassifications	0	0
Sales	0	0
Net unrealized gains (losses) included in net income	(366)	(3,282)
Financial assets at end of period	3,412	3,778
Recurring fair value measurements \| Digital gold strategies \| Level 3
Changes in fair value measurement, assets [abstract]
Financial assets at beginning of period	3,778	7,060
Purchases and reclassifications	0	0
Sales	0	0
Net unrealized gains (losses) included in net income	(366)	(3,282)
Financial assets at end of period	$ 3,412	$ 3,778

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The amount of assets that are: (a) cash; (b) an equity instrument of another entity; (c) a contractual right: (i) to receive cash or another financial asset from another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially favourable to the entity; or (d) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to receive a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose the entity’s own equity instruments do not include puttable financial instruments classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. [Refer: Financial instruments, class [member]; Financial liabilities]

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The gains (losses) including exchange differences recognised in profit or loss on the fair value measurement of assets. [Refer: At fair value [member]]

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The amount of increase (decrease) in the fair value measurement of assets, recognised in profit or loss before tax, due to a reasonably possible decrease in an unobservable input. [Refer: Tax income (expense)]

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The amount of increase (decrease) in the fair value measurement of assets, recognised in profit or loss before tax, due to a reasonably possible increase in an unobservable input. [Refer: Tax income (expense)]

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The percentage of a reasonably possible decrease in an unobservable input used in fair value measurement of assets.

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The percentage of a reasonably possible increase in an unobservable input used in fair value measurement of assets.

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The decrease in the fair value measurement of assets resulting from settlements. [Refer: At fair value [member]]

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The amount of transfers out of Level 2 and into Level 1 of the fair value hierarchy of assets held at the end of the reporting period. [Refer: Level 1 of fair value hierarchy [member]; Level 2 of fair value hierarchy [member]]

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Purchases (Reclassifications), Fair Value Measurement, Assets

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