Fair value measurements - Schedule of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Available-for-sale securities [Abstract]
Cost	$ 12,001	$ 11,755	$ 11,693
Gross Unrealized Gains	115	45	11
Gross Unrealized Losses	312	478	773
Fair Value	11,804	11,322	10,931
Mortgage-backed securities
Available-for-sale securities [Abstract]
Cost	8,104	8,234	8,386
Gross Unrealized Gains	41	17	0
Gross Unrealized Losses	312	470	750
Fair Value	7,833	7,781	7,636
U.S. Treasury securities
Available-for-sale securities [Abstract]
Cost	3,897	3,521	3,307
Gross Unrealized Gains	74	28	11
Gross Unrealized Losses	0	8	23
Fair Value	$ 3,971	$ 3,541	$ 3,295