Segment Information (Details) - Reconciliation of Operating Profit (Loss) from Segments to Consolidated - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Operating loss:
Operating profit (loss)	$ (10,922)	$ (2,817)
Frequency Electronics Inc New York [Member]
Operating loss:
Operating profit (loss)	(9,910)	(4,429)
Frequency Electronics Inc Zyfer [Member]
Operating loss:
Operating profit (loss)	(673)	1,730
Corporate Segment [Member]
Operating loss:
Operating profit (loss)	$ (339)	$ (118)