Income Taxes - Tax Effects of Temporary Differences That Give Rise to Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Apr. 30, 2019
Deferred tax assets
Accruals and expenses not deducted for tax purposes	$ 363	$ 328
State net operating loss carryforwards	226	217
Fixed asset basis differences	822	831
Nonqualified stock options	848	858
Right of use liability	547
Tax credit carryforwards	83
Total gross deferred tax assets	2,889	2,234
Less valuation allowance	(190)	(160)
Net deferred tax	2,699	2,074
Deferred tax liabilities
Capitalized computer software development costs	(2,090)	(2,766)
Net gains/losses on trading securities	(1,005)	(1,183)
Goodwill and intangible assets basis differences	(746)	(639)
Right of use asset	(513)
Deferred agent commissions	(1,242)	(1,000)
Total gross deferred tax liabilities	(5,596)	(5,588)
Net deferred tax liabilities	$ (2,897)	$ (3,514)