XML 29 R18.htm IDEA: XBRL DOCUMENT v3.8.0.1
Prepaid Expenses and Other Current Assets (Tables)
3 Months Ended
Mar. 31, 2018
Prepaid Expenses And Other Current Assets [Abstract]  
Schedule of prepaid expenses and other current assets
    December 31,     March 31,  
    2017     2018  
Research and development tax credit receivable   $ 1,054     $ 1,278  
Prepayments and VAT receivable     772       1,045  
Other current assets     238       684  
    $ 2,064     $ 3,007