Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	May 01, 2019	Apr. 30, 2019
Accounting Policies [Abstract]
Net (loss) income	$ 307	$ (641)	$ 267	$ 483	$ (334)	$ 750
Net cash used in operating activities	(360)				(81)	(400)
Accumulated deficit	71,032				71,032			$ 70,698
Working capital deficit	1,200				1,200
Cash and cash equivalents	2,784				2,784			3,237
Unrecognized tax benefits	151				151			151
Provision for income taxes	11		$ 1		26	$ 1
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, net	3,004				3,004			$ 0
Present value of minimum payments due	$ 10,833				$ 10,833
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, net							$ 3,200
Deferred rent							900
Operating lease liability							4,100
Present value of minimum payments due							$ 4,100