Fair Value Measurements - Net Asset Value (Details) - USD ($) $ in Millions	Apr. 27, 2019	Apr. 28, 2018
Fair Value Measured Using Net Asset Value
Assets
Marketable securities	$ 7.7	$ 6.7

Amount of investment in marketable security.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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