Other Assets and Liabilities - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other Non-Current Liabilities:
Provision for retirement indemnity	$ 1,340	$ 1,303
Customer allowances	1,700	1,636
Unrecognized tax benefits	4,229	3,954
Guarantee	6,174	0
Other	809	191
Total	$ 14,252	$ 7,084