Other Assets and Liabilities - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Non-Current Liabilities:
Provision for retirement indemnity	$ 1,262	$ 1,303
Customer allowances	1,596	1,636
Unrecognized tax benefits	4,720	3,954
Guarantee	5,851	0
Other	721	191
Total	$ 14,150	$ 7,084