Defined Contribution Plan - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
Jul. 29, 2017	Jul. 30, 2016
Defined Contribution Plan Disclosure [Line Items]
Company contributions, employee benefit expenses	$ 3,049	$ 3,387

Amount of cost for defined contribution plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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