Tax Effects of Temporary Differences That Give Rise to Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Apr. 30, 2017	Apr. 30, 2016
Deferred tax assets:
Accruals and expenses not deducted for tax purposes	$ 461	$ 1,008
State net operating loss carryforwards	295	333
Fixed asset basis differences	1,384	1,515
Nonqualified stock options	1,679	1,870
Deferred revenue	234	96
Total gross deferred tax assets	4,054	4,822
Less valuation allowance	166	459
Net deferred tax assets	3,887	4,363
Deferred tax liabilities:
Capitalized computer software development costs	(3,298)	(3,500)
Net gains/losses on trading securities	(1,019)	(673)
Goodwill and intangible assets basis differences	(939)	(957)
Deferred agent commissions	(625)	(553)
Total gross deferred tax liabilities	(5,881)	(5,682)
Net deferred tax liabilities	$ (1,994)	$ (1,319)