Note 11 - Business Segment Information - Domestic and International Revenue by Segment (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Revenues	[1]	$ 30,373	$ 25,973
UNITED STATES
Revenues	[1]	$ 15,692	$ 14,058
Revenue, percentage	[1]	52.00%	54.00%
Non-US [Member]
Revenues	[1]	$ 14,681	$ 11,915
Revenue, percentage	[1]	48.00%	46.00%
Battery & Energy Products Segment [Member]
Revenues	[1]	$ 29,150	$ 22,111
Battery & Energy Products Segment [Member] | UNITED STATES
Revenues	[1]	14,540	12,590
Battery & Energy Products Segment [Member] | Non-US [Member]
Revenues	[1]	14,610	9,521
Communications Systems Segment [Member]
Revenues	[1]	1,223	3,862
Communications Systems Segment [Member] | UNITED STATES
Revenues	[1]	1,152	1,468
Communications Systems Segment [Member] | Non-US [Member]
Revenues	[1]	$ 71	$ 2,394

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