Income Taxes - Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
United States federal corporate income tax rate	34.00%
Increase (decrease) in income taxes resulting from:
Income tax (benefit) expense at Federal statutory income tax rate	$ (3,379)	$ (670)	$ 906
State income tax expense, net of federal benefit	56	(156)	(37)
State research and development, investment credits	(435)	(363)	(317)
Non-deductible meals & entertainment	47	49	33
Non-deductible stock compensation expense	338	216	181
Non-deductible transaction costs	0	116	260
Subpart F income, net of foreign tax credits	1,171	523	61
Manufacturing deduction	0	0	(102)
Nontaxable interest income	0	(162)	(106)
Foreign tax rate differential	(902)	(1,258)	(792)
Federal research and development credits	(427)	(395)	(348)
Uncertain tax positions	189	283	(413)
Change in tax rates	8	(95)	80
Change in tax rates	926	14	(313)
Change in valuation allowance	3,330	7,425	1,392
Income tax expense	1,096	5,547	413
Foreign Research and Development Incentives [Member]
Increase (decrease) in income taxes resulting from:
Other	(22)	(45)	(59)
Other Deductions [Member]
Increase (decrease) in income taxes resulting from:
Other	(196)	(13)	(13)
SAUDI ARABIA
Increase (decrease) in income taxes resulting from:
Foreign tax rate differential	$ 0	$ 52	$ 0