Organization and Principal Activities - reconciliation of cash, cash equivalents and restricted cash reported (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 6,888	$ 3,921
Restricted cash	2,778	808
Total cash, cash equivalents, and restricted cash	$ 9,666	$ 4,729	$ 35,126	$ 2,184