Defined Contribution Plan - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Oct. 27, 2018	Oct. 28, 2017	Oct. 27, 2018	Oct. 28, 2017
Defined Contribution Plan Disclosure [Line Items]
Company contributions, employee benefit expenses	$ 2,419	$ 2,789	$ 5,151	$ 5,838

Amount of cost for defined contribution plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration