Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended				6 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Apr. 30, 2020	May 01, 2019
Accounting Policies [Abstract]
Cash equivalents	$ 0				$ 0		$ 0
Net income (loss)	1,000	$ 75,000	$ 307,000	$ (641,000)	76,000	$ (334,000)
Net cash provided by (used in) operating activities					164,000	81,000
Accumulated deficit	72,597,000				72,597,000		72,673,000
Working capital deficit	2,200,000				2,200,000
Cash and cash equivalents	8,553,000				8,553,000		8,342,000
Unrecognized tax benefits	180,000				180,000		178,000
Provision for income taxes	15,000		$ 11,000		28,000	$ 26,000
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, net	$ 5,527,000				$ 5,527,000		$ 2,798,000
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, net								$ 3,200,000
Deferred rent								900,000
Operating lease liability								$ 4,100,000