Income Taxes - Effective Income Tax Expense (Benefit) Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Statutory amount (computed at 35%)	$ (1,449)	$ (714)	$ (3,703)
Re-measurement of deferred tax assets	(7,451)	0	0
Valuation allowance on foreign tax credits	1,514	0	0
State income tax, net of federal benefit	168	94	(709)
Permanent differences, other	505	99	43
Permanent differences, incentive stock options	447	224	298
True up to prior years	188	109	0
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(77)	1,769	1,552
Balance at the end of year	1,614	0
Total	$ (4,541)	$ 1,581	$ (2,519)
Consolidated effective tax rate	109.70%	(77.50%)	23.80%