Note 7 - Income Taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Net operating loss carryforwards	$ 11,227	$ 8,604
Stock-based compensation	1,040	1,179
Other accruals and reserves	1,924	1,663
Credits	10,857	11,781
Foreign	457	399
Accrued warranty	1,863	847
Depreciation and amortization	2,024	1,592
Other	282	303
Deferred tax asset before valuation allowance	29,674	26,368
Valuation allowance	(27,865)	(7,242)
Deferred tax asset after valuation allowance	1,809	19,126
Deferred tax liability	(1,269)
Deferred tax liability on goodwill	(83)	(71)
Net deferred tax asset	$ 457	$ 19,055