Note 6 - Revenue From Contracts with Customers - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net revenues	$ 18,871	$ 14,180
Semiconductor Market [Member]
Net revenues	10,539	10,439
Industrial Market [Member]
Net revenues	5,653	120
Telecommunications Market [Member]
Net revenues	1,279	2,695
Other Non-semiconductors Markets [Member]
Net revenues	1,400	926
Thermal Testing Products [Member]
Net revenues	6,032	6,822
Induction Heating Products [Member]
Net revenues	5,622
Semiconductor Production Test Products [Member]
Net revenues	5,339	6,162
Service and Other Products [Member]
Net revenues	1,878	1,196
End User [Member]
Net revenues	16,328	12,486
OEM and Integrators [Member]
Net revenues	$ 2,543	$ 1,694