Investments - Available for sale securities (Details) - Available-for-sale securities $ in Thousands	3 Months Ended
Jul. 27, 2019 USD ($)
Investments
Sales or Purchases	$ 2,693
Carrying Value	2,693
Investment in limited partnership fund
Investments
Sales or Purchases	2,693
Carrying Value	$ 2,693

Amount of investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant