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Revenue Recognition and Contracts with Customers - Schedule of Adjustments to Condensed Consolidated Balance Sheet on Adoption of ASU 2014-09 (Detail) - USD ($) $ in Thousands	Jul. 31, 2018	May 01, 2018	Apr. 30, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accrued expenses	$ 37,524		$ 41,632
Deferred revenue from contracts with customers	13,621		23,305
Deferred taxes			12,895
Retained earnings	$ 392,181		$ 389,146
ASU 2014-09
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accrued expenses		$ 24,456
Deferred revenue from contracts with customers		23,305
Deferred taxes		11,376
Retained earnings		384,536
ASU 2014-09 \| Accounting Standard Adjustments
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accrued expenses		(17,176)
Deferred revenue from contracts with customers		23,305
Deferred taxes		(1,519)
Retained earnings		$ (4,610)