Note 3 - Revenue From Contracts With Customers - Revenues Disaggregated (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues from external customers	$ 23,009	$ 21,966
North America [Member]
Revenues from external customers	15,465	14,397
Europe [Member]
Revenues from external customers	4,452	4,618
Asia [Member]
Revenues from external customers	3,039	2,848
Other Regions [Member]
Revenues from external customers	53	103
Transferred at Point in Time [Member]
Revenues from external customers	18,703	18,067
Transferred over Time [Member]
Revenues from external customers	4,306	3,899
Power and Electromechanical Segment [Member]
Revenues from external customers	17,551	17,020
Power and Electromechanical Segment [Member] | North America [Member]
Revenues from external customers	13,641	13,032
Power and Electromechanical Segment [Member] | Europe [Member]
Revenues from external customers	889	1,094
Power and Electromechanical Segment [Member] | Asia [Member]
Revenues from external customers	3,020	2,819
Power and Electromechanical Segment [Member] | Other Regions [Member]
Revenues from external customers	1	75
Power and Electromechanical Segment [Member] | Transferred at Point in Time [Member]
Revenues from external customers	17,551	17,020
Power and Electromechanical Segment [Member] | Transferred over Time [Member]
Revenues from external customers
Energy Segment [Member]
Revenues from external customers	5,458	4,946
Energy Segment [Member] | North America [Member]
Revenues from external customers	1,824	1,365
Energy Segment [Member] | Europe [Member]
Revenues from external customers	3,563	3,524
Energy Segment [Member] | Asia [Member]
Revenues from external customers	19	29
Energy Segment [Member] | Other Regions [Member]
Revenues from external customers	52	28
Energy Segment [Member] | Transferred at Point in Time [Member]
Revenues from external customers	1,152	1,047
Energy Segment [Member] | Transferred over Time [Member]
Revenues from external customers	4,306	3,899
Distributor Sales [Member]
Revenues from external customers	9,430	9,617
Distributor Sales [Member] | Power and Electromechanical Segment [Member]
Revenues from external customers	9,430	9,617
Distributor Sales [Member] | Energy Segment [Member]
Revenues from external customers
Direct Sales [Member]
Revenues from external customers	13,579	12,349
Direct Sales [Member] | Power and Electromechanical Segment [Member]
Revenues from external customers	8,121	7,403
Direct Sales [Member] | Energy Segment [Member]
Revenues from external customers	$ 5,458	$ 4,946