CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	May 31, 2020	May 26, 2019	May 27, 2018
Income Statement [Abstract]
Product sales	$ 590,366	$ 557,559	$ 524,227
Cost of product sales	515,378	476,556	445,889
Gross profit	74,988	81,003	78,338
Operating costs and expenses:
Research and development	11,099	11,466	12,800
Selling, general and administrative	72,188	62,062	51,951
Impairment of goodwill and intangible assets	12,953	2,000	0
Restructuring costs	17,285	0	0
Total operating costs and expenses	113,525	75,528	64,751
Operating (loss) income	(38,537)	5,475	13,587
Dividend income	1,125	1,650	1,650
Interest income	103	145	211
Interest expense, net	(9,603)	(5,230)	(1,950)
Other (expense) income	(4,395)	1,600	2,900
Net (loss) income from continuing operations before taxes	(51,307)	3,640	16,398
Income tax benefit (expense)	13,116	(1,518)	9,363
Net (loss) income from continuing operations	(38,191)	2,122	25,761
Discontinued operations:
Loss from discontinued operations	0	(2,238)	(1,188)
Income tax benefit	0	527	350
Loss from discontinued operations, net of tax	0	(1,711)	(838)
Consolidated net (loss) income	(38,191)	411	24,923
Non-controlling interest expense	0	0	(94)
Net (loss) income applicable to common stockholders	$ (38,191)	$ 411	$ 24,829
Basic net (loss) income per share:
(Loss) income from continuing operations (in dollars per share)	$ (1.31)	$ 0.07	$ 0.93
Loss from discontinued operations (in dollars per share)	0	(0.06)	(0.03)
Total basic net (loss) income per share (in dollars per share)	(1.31)	0.01	0.90
Diluted net (loss) income per share:
(Loss) income from continuing operations (in dollars per share)	(1.31)	0.07	0.92
Loss from discontinued operations (in dollars per share)	0	(0.06)	(0.03)
Total diluted net (loss) income per share (in dollars per share)	$ (1.31)	$ 0.01	$ 0.89
Shares used in per share computation:
Basic (in shares)	29,162	28,359	27,535
Diluted (in shares)	29,162	28,607	27,915
Revenue, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Cost, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember