Other Assets and Liabilities - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Other Non-Current Liabilities:
Provision for retirement indemnity	$ 1,271	$ 1,303
Customer allowances	1,764	1,636
Unrecognized tax benefits	4,229	3,954
Guarantee	5,985	0
Other	740	191
Total	$ 13,989	$ 7,084