Balance Sheet Information - Accrued expenses and other payables (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balance Sheet Information
Accrued selling, general and administrative expenses	$ 2,221	$ 4,246
Accrued salary and bonus	2,919	646
Accrued employee benefits	727	754
Accrued cost of service	1,187	1,566
Accrued taxes (including VAT)	3,685	4,193
Accrued interest payable	347	328
Accrued customer credit	879	77
Other accrued expenses	2,832	1,234
Accrued expenses and other payables	$ 14,797	$ 13,044