Presentation and Summary of Significant Accounting Policies - Summary of Effect of Adopting Topic 606 on Condensed Consolidated Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net earnings	$ 6,803
Deferred income taxes	320	$ 621	$ 675
Changes in operating assets and liabilities:
Accounts receivable, net	2,165	(1,774)	1,187
Prepaid expenses and other assets	536	(1,983)	(284)
Accounts payable and other liabilities	(3,611)	$ (1,807)	$ 1,185
Deferred revenue	431
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net earnings	542
Deferred income taxes	66
Changes in operating assets and liabilities:
Accounts receivable, net	(151)
Prepaid expenses and other assets	64
Accounts payable and other liabilities	0
Deferred revenue	(521)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net earnings	7,345
Deferred income taxes	386
Changes in operating assets and liabilities:
Accounts receivable, net	2,014
Prepaid expenses and other assets	600
Accounts payable and other liabilities	(3,611)
Deferred revenue	$ (90)