Presentation and Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Apr. 30, 2022 USD ($)	Apr. 30, 2022 USD ($)	Apr. 30, 2022 USD ($) segment	Apr. 30, 2022 USD ($) Group	Apr. 30, 2022 USD ($) CompensationPlan	Apr. 30, 2022 USD ($) $ / shares	Apr. 30, 2022 USD ($) Segment	Apr. 30, 2021 USD ($)	Apr. 30, 2020 USD ($)
Accounting Policies [Line Items]
Number of reportable segments			3				3
Number of major product and service groups | Group				6
Number of major business segments | segment			3
Amounts received for reimbursement of travel and other out-of-pocket expenses		$ 171,000						$ 26,000	$ 1,500,000
Revenue recognized and included in deferred revenue		37,100,000
Remaining performance obligations	$ 134,000,000	134,000,000	$ 134,000,000	$ 134,000,000	$ 134,000,000	$ 134,000,000	$ 134,000,000
Deferred commissions	3,400,000	3,400,000	3,400,000	3,400,000	3,400,000	3,400,000	3,400,000	3,900,000
Amortization of sales commissions		2,100,000						2,000,000	2,100,000
Impairment loss		0						0	0
Unbilled	2,989,000	2,989,000	2,989,000	2,989,000	2,989,000	2,989,000	2,989,000	2,201,000
Cash equivalents	98,500,000	98,500,000	98,500,000	98,500,000	98,500,000	98,500,000	98,500,000	81,700,000
Total amounts of expense/(recovery) to operations for doubtful accounts		0						0	97,000
Depreciation and amortization expense		700,000						600,000	600,000
Amortization of acquisition-related intangibles		212,000						212,000	285,000
Lease right of use assets	935,000	935,000	935,000	935,000	935,000	935,000	935,000	1,454,000
Operating lease obligations	541,000	541,000	541,000	541,000	541,000	541,000	541,000	739,000
Long-term operating lease obligations	461,000	461,000	461,000	461,000	$ 461,000	461,000	461,000	821,000
Total revenues		127,553,000						111,408,000	115,466,000
Number of stock compensation plans | CompensationPlan					1
Stock-based compensation expense		3,956,000						2,546,000	2,027,000
Income tax benefit (shortfall)		1,700,000						600,000	700,000
Advertising expense		3,000,000						2,100,000	2,900,000
Liability for warranty agreements	$ 0	0	0	0	$ 0	$ 0	0	0
Computers Equipment And Software
Accounting Policies [Line Items]
Estimated useful lives of assets	3 years
Office furniture and equipment
Accounting Policies [Line Items]
Estimated useful lives of assets	7 years
Buildings and leasehold improvements
Accounting Policies [Line Items]
Estimated useful lives of assets	15 years
Buildings
Accounting Policies [Line Items]
Estimated useful lives of assets	30 years
Operating Expense
Accounting Policies [Line Items]
Amortization of acquisition-related intangibles		200,000						200,000	300,000
Cost of License Fees
Accounting Policies [Line Items]
Amortization of acquisition-related intangibles								600,000	1,300,000
Class A Common Shares
Accounting Policies [Line Items]
Dividends preference (in usd per share) | $ / shares						$ 0.05
Capitalized Software
Accounting Policies [Line Items]
Intangible assets amortized period	3 years
Finite-Lived Intangible Assets
Accounting Policies [Line Items]
Amortization of acquisition-related intangibles								800,000	$ 1,600,000
License Fees
Accounting Policies [Line Items]
Unbilled	$ 1,000,000	1,000,000	1,000,000	1,000,000	1,000,000	$ 1,000,000	1,000,000	700,000
Services Revenues
Accounting Policies [Line Items]
Unbilled	$ 2,000,000	$ 2,000,000	$ 2,000,000	$ 2,000,000	$ 2,000,000	$ 2,000,000	$ 2,000,000	$ 1,500,000
Minimum
Accounting Policies [Line Items]
Contractual period of maintenance contract	1 year
Minimum | Other Intangible Assets
Accounting Policies [Line Items]
Intangible assets amortized period	1 year
Maximum
Accounting Policies [Line Items]
Contractual period of maintenance contract	3 years
Maximum | Other Intangible Assets
Accounting Policies [Line Items]
Intangible assets amortized period	8 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-05-01
Accounting Policies [Line Items]
Revenue recognition of remaining performance obligations	47.00%	47.00%	47.00%	47.00%	47.00%	47.00%	47.00%
Revenue recognition in next twelve months	12 months	12 months	12 months	12 months	12 months	12 months	12 months