Organization, Use of Estimates and Basis of Presentation - Narrative (Details)	3 Months Ended			6 Months Ended
	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Oct. 31, 2018 USD ($) subsidiary	Oct. 31, 2017 USD ($)	Apr. 30, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating subsidiaries | subsidiary				2
Restricted cash	$ 0			$ 0		$ 150,000
Net income (loss)	267,000	$ 483,000	$ (94,000)	750,000	$ (768,000)
Net cash used in operating activities				(400,000)	1,680,000
Accumulated deficit	(70,076,000)			(70,076,000)		(70,826,000)
Positive working capital	411,000			411,000
Cash and cash equivalents	2,000,000			2,000,000
Unrecognized tax benefits	151,000			151,000		$ 151,000
Provision for income taxes	$ 1,000		$ 11,000	$ 1,000	$ 15,000