Income taxes - Cash paid for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income taxes
Total income taxes paid, net of refunds	$ 714	$ 1,482	$ 16
Federal
Income taxes
US Federal	442	1,248
State
Income taxes
US state and local	272	234	16
Massachusetts
Income taxes
US state and local	270	232	$ 16
Other
Income taxes
US state and local	$ 2	$ 2

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Amount, after refund, of cash paid to foreign, federal, state, and local jurisdictions as income tax.

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