Note 5 - Goodwill and Intangible Assets - Changes in the Amount of the Carrying Value of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Balance	$ 1,706
Acquisition of Ambrell	12,032
Balance	13,738	$ 1,706
Sigma [Member]
Balance	1,656
Balance	1,656	1,656
Thermonics [Member]
Balance	50
Balance	50	50
Ambrell [Member]
Balance
Acquisition of Ambrell	12,032
Balance	$ 12,032