Income taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Taxes [Line Items]
Swiss federal statutory rate	8.50%	8.50%	8.50%
Effective corporate tax	13.40%
Valuation allowance, deferred tax asset, increase (decrease), amount	$ 196,694	$ 1,261,855
Deferred income tax liability	1,300
Non-U.S NOLs	27,377
NOLs carry forwards indefinitely	2,531
Uncertain tax positions, interest and penalties recognized	1	$ 0	$ 2
Swiss Federal Tax Administration (FTA)
Income Taxes [Line Items]
Federal NOLs	1,236,560
State and local jurisdiction | Swiss Federal Tax Administration (FTA)
Income Taxes [Line Items]
Federal NOLs	$ 1,208,800