Note 3 - Revenue From Contracts With Customers - Revenues Disaggregated (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues from external customers	$ 23,127	$ 22,500	$ 45,093	$ 40,345
North America [Member]
Revenues from external customers	15,785		30,182
Europe [Member]
Revenues from external customers	3,156		7,774
Asia [Member]
Revenues from external customers	4,135		6,984
Other Regions [Member]
Revenues from external customers	51		153
Transferred at Point in Time [Member]
Revenues from external customers	21,206		39,273
Transferred over Time [Member]
Revenues from external customers	1,921		5,820
Power and Electromechanical Segment [Member]
Revenues from external customers	20,320	18,180	37,340	31,842
Power and Electromechanical Segment [Member] | North America [Member]
Revenues from external customers	15,057		28,089
Power and Electromechanical Segment [Member] | Europe [Member]
Revenues from external customers	1,098		2,192
Power and Electromechanical Segment [Member] | Asia [Member]
Revenues from external customers	4,130		6,949
Power and Electromechanical Segment [Member] | Other Regions [Member]
Revenues from external customers	35		110
Power and Electromechanical Segment [Member] | Transferred at Point in Time [Member]
Revenues from external customers	20,320		37,340
Power and Electromechanical Segment [Member] | Transferred over Time [Member]
Revenues from external customers
Energy Segment [Member]
Revenues from external customers	2,807	$ 4,320	7,753	$ 8,503
Energy Segment [Member] | North America [Member]
Revenues from external customers	728		2,093
Energy Segment [Member] | Europe [Member]
Revenues from external customers	2,058		5,582
Energy Segment [Member] | Asia [Member]
Revenues from external customers	5		35
Energy Segment [Member] | Other Regions [Member]
Revenues from external customers	16		43
Energy Segment [Member] | Transferred at Point in Time [Member]
Revenues from external customers	886		1,933
Energy Segment [Member] | Transferred over Time [Member]
Revenues from external customers	1,921		5,820
Distributor Sales [Member]
Revenues from external customers	12,161		21,778
Distributor Sales [Member] | Power and Electromechanical Segment [Member]
Revenues from external customers	12,161		21,778
Distributor Sales [Member] | Energy Segment [Member]
Revenues from external customers
Direct Sales [Member]
Revenues from external customers	10,966		23,315
Direct Sales [Member] | Power and Electromechanical Segment [Member]
Revenues from external customers	8,159		15,562
Direct Sales [Member] | Energy Segment [Member]
Revenues from external customers	$ 2,807		$ 7,753