Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Components of provision for income taxes
Income tax expense	$ 707	$ 619	$ 1,949	$ 1,761
Current foreign tax expense	291	125	631	486
Current federal tax expense		(6)		30
Current state tax expense	$ 416	$ 500	$ 1,318	$ 1,245

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