Presentation and Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2020 USD ($)	Jan. 31, 2020 USD ($)	Oct. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)	Apr. 30, 2019 USD ($)	Jan. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Apr. 30, 2020 USD ($) Segment CompensationPlan Group $ / shares	Apr. 30, 2019 USD ($)	Apr. 30, 2018 USD ($)	May 01, 2019 USD ($)
Accounting Policies [Line Items]
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									$ 1,500	$ 1,400	$ 1,900
Revenue recognized and included in deferred revenue									31,000
Unbilled	$ 2,425				$ 1,475				2,425	1,475
Cash equivalents	75,300				56,600				75,300	56,600
Total amounts of expense/(recovery) to operations for doubtful accounts									97	0	24
Depreciation and amortization expense									600	700	500
Amortization of acquisition-related intangibles									285	388	580
Remaining performance obligations	77,000								77,000
Deferred commissions	3,500				2,300				3,500	2,300
Amortization of sales commissions									2,100
Total revenues	$ 29,273	$ 30,600	$ 28,210	$ 27,383	26,271	$ 27,003	$ 28,033	$ 27,399	$ 115,466	108,706	112,703
Period of economic benefit	6 years								6 years
Lease right of use assets	$ 2,053								$ 2,053
Current lease liabilities	763								763
Long-term operating lease obligations	1,424								$ 1,424
Number of stock compensation plans | CompensationPlan									1
Stock-based compensation expense									$ 2,027	1,751	1,467
Income tax benefit (shortfall)									700	300	39
Advertising expense									$ 2,900	2,300	2,400
Number of reportable segments | Segment									3
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
Building
Accounting Policies [Line Items]
Estimated useful lives of assets									30 years
Operating Expense
Accounting Policies [Line Items]
Amortization of acquisition-related intangibles									$ 300	400	600
Cost of License Fees
Accounting Policies [Line Items]
Amortization of acquisition-related intangibles									$ 1,300	2,000	1,200
Class A Common Shares
Accounting Policies [Line Items]
Dividends preference (in usd per share) | $ / shares									$ 0.05
Accounting Standards Update 2016-02
Accounting Policies [Line Items]
Lease right of use assets												$ 2,700
Current lease liabilities												700
Long-term operating lease obligations												2,100
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Accounting Policies [Line Items]
Total revenues									$ 1,200
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09
Accounting Policies [Line Items]
Upfront recognition of revenue									70.00%
Sales commission capitalized	1,100								$ 1,100
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									$ 1,600	2,400	$ 1,800
License Fees
Accounting Policies [Line Items]
Unbilled	1,300				400				1,300	400
Services Revenues
Accounting Policies [Line Items]
Unbilled	$ 1,100				$ 1,100				$ 1,100	$ 1,100
Minimum
Accounting Policies [Line Items]
Contractual period of maintenance contract									1 year
Minimum | Accounting Standards Update 2016-02
Accounting Policies [Line Items]
Lease right of use assets												28,000
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 | Accounting Standards Update 2016-02
Accounting Policies [Line Items]
Lease right of use assets												$ 30,000
Maximum | Other Intangible Assets
Accounting Policies [Line Items]
Intangible assets amortized period									8 years