Note 12 - Business Segment Information - Revenue by Business Segment Sector (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Revenue	[1]	$ 25,814	$ 18,882
Revenue, percentage	[1]
Commercial [Member]
Revenue		$ 14,802	$ 10,010
Revenue, percentage		57.00%	53.00%
Government & Defense [Member]
Revenue		$ 11,012	$ 8,872
Revenue, percentage		43.00%	47.00%
Battery & Energy Products Segment [Member]
Revenue	[1]	$ 20,761	$ 15,998
Battery & Energy Products Segment [Member] | Commercial [Member]
Revenue		14,802	10,010
Battery & Energy Products Segment [Member] | Government & Defense [Member]
Revenue		5,959	5,988
Communications Systems Segment [Member]
Revenue	[1]	5,053	2,884
Communications Systems Segment [Member] | Commercial [Member]
Revenue
Communications Systems Segment [Member] | Government & Defense [Member]
Revenue		$ 5,053	$ 2,884

[1] Sales classified to U.S. include shipments to U.S.-based prime contractors which in some cases may serve non-U.S. projects