Presentation and Summary of Significant Accounting Policies - Summary of Effect of Adopting Topic 606 on Condensed Consolidated Statement of Cash Flows (Detail) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2019	Jan. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net earnings (loss)	$ 4,929	$ 10,785
Deferred income taxes	(166)	208
Changes in operating assets and liabilities:
Accounts receivable, net	(831)	(2,926)
Prepaid expenses and other assets	724	(1,494)
Accounts payable and other liabilities	(4,031)	(999)
Deferred revenue	94	$ 4,096
Balances under Prior GAAP
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net earnings (loss)	5,207
Deferred income taxes	(122)
Changes in operating assets and liabilities:
Accounts receivable, net	(932)
Prepaid expenses and other assets	756
Accounts payable and other liabilities	(4,031)
Deferred revenue	(159)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net earnings (loss)	278
Deferred income taxes	44
Changes in operating assets and liabilities:
Accounts receivable, net	(101)
Prepaid expenses and other assets	32
Accounts payable and other liabilities	0
Deferred revenue	$ (253)