Note 13 - Acquisition (Details Textual)		3 Months Ended		6 Months Ended
	Feb. 01, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Business Combination, Acquisition Related Costs		$ 19,000		$ 1,089,000
Revenue from Contract with Customer, Including Assessed Tax		49,019,000	37,886,000	91,949,000	74,939,000
Net Income (Loss) Attributable to Parent, Total		$ 3,990,000	$ 2,630,000	5,767,000	$ 4,801,000
Dielectrics [Member]
Lessee, Operating Lease, Term of Contract	5 years
Number of Lease Term Options	2
Dielectrics [Member]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Payments to Acquire Businesses, Gross	$ 80,000,000
Business Combination, Consideration Transferred, Working Capital Adjustment	$ 250,000
Business Combination, Acquisition Related Costs				1,100,000
Revenue from Contract with Customer, Including Assessed Tax				15,600,000
Net Income (Loss) Attributable to Parent, Total				$ 1,900,000