Accounts Receivable, Net and Revenue Concentrations - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Allowance for Doubtful Accounts
Balance at beginning of period	$ 1,064	$ 904
Additions to costs and expenses	4	23
(Write-offs)/Foreign exchange effects	9	18
Balance at end of period	$ 1,077	$ 945