Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Apr. 30, 2021 USD ($) segment	Apr. 30, 2020 USD ($)	Apr. 30, 2019 USD ($)	Apr. 01, 2021 USD ($)	May 01, 2020 USD ($)	May 01, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Accrued liabilities			$ (316,000)	$ 1,440,000
Net income (loss)	$ 959,000	$ 1,035,000	362,000	(2,093,000)
Total stockholders' equity	8,086,000	8,086,000	7,428,000	5,099,000	$ 2,137,000
Cash			4,687,000	8,342,000
Cash equivalents			0	0
Working capital			1,400,000
Impairment of long-lived assets			$ 0	0
Number of reportable segments | segment			1
Goodwill Impairment			$ 0	335,000
Goodwill			335,000	335,000
Unrecognized tax benefits			181,000	178,000	151,000
Income tax penalties and interest expense			3,000	27,000,000
Provision for (benefit) from income tax			75,000	130,000
Operating lease right-of-use assets, net			$ 8,521,000	2,798,000			$ 2,798,000
Operating lease, liability						$ 3,300,000
Revision of Prior Period, Adjustment
Property, Plant and Equipment [Line Items]
Accrued liabilities					101,000
Net income (loss)	219,000	219,000		(118,000)
Total stockholders' equity	$ 219,000	$ 219,000		$ (219,000)	$ (101,000)
Accounting Standards Update 2016-02
Property, Plant and Equipment [Line Items]
Operating lease right-of-use assets, net								$ 3,200,000
Advance rent								900,000
Operating lease, liability								$ 4,100,000
Minimum
Property, Plant and Equipment [Line Items]
Useful life			3 years
Maximum
Property, Plant and Equipment [Line Items]
Useful life			9 years