Reserve for Severance Activity in reserve (Details) - Employee Severance [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reserve for severance and related payments
Balance at beginning of period	$ 1,710	$ 697	$ 311
Charged to earnings current year	738	2,376	1,273
Cash paid and exchange rate variance	(1,965)	(1,363)	(887)
Balance at end of the period	$ 483	$ 1,710	$ 697