Note 8 - Income Taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Net operating loss carryforwards	$ 8,604	$ 15,487
Stock-based compensation	1,179	1,486
Other accruals and reserves	1,663	2,160
Credits	11,781	9,006
Foreign	399	377
Accrued warranty	847	890
Depreciation and amortization	1,592	2,627
Other	303	95
Deferred tax asset before valuation allowance	26,368	32,128
Valuation allowance	(7,242)	(31,751)
Deferred tax asset after valuation allowance	19,126	377
Deferred tax liability on goodwill	(71)	(85)
Net deferred tax asset	$ 19,055	$ 292