Employees' Defined Contribution Plan (Details) - USD ($) $ in Thousands	12 Months Ended
Apr. 27, 2019	Apr. 28, 2018	Apr. 29, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company contributions, employee benefit expenses	$ 6,702	$ 7,196	$ 4,828

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

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