Fair value measurements (Details) - Recurring - USD ($) $ in Thousands	Jun. 27, 2020	Mar. 28, 2020	Jun. 29, 2019
Assets
Total assets	$ 5,350	$ 5,066	$ 5,673
Other current assets
Assets
Nonqualified retirement plan	$ 5,350	$ 5,066	$ 5,673

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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