Contract assets and liabilities (Details 5) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Contract assets and liabilities
Trading and manufacturing (revenue recognized at point in time)	$ 9,549	$ 12,143	$ 9,332
Engineering (revenue recognized over time)	5,834	5,797	5,617
Revenue	$ 15,383	$ 17,940	$ 14,949

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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+ Details