Discontinued Operations (Details)				3 Months Ended
	Feb. 22, 2019 USD ($)	Jul. 29, 2018 USD ($)	Jun. 29, 2018 USD ($)	Jul. 27, 2019 USD ($) contract	Jul. 28, 2018 USD ($)
Discontinued operations
Amount of recall and other damages sought	$ 6,500,000
Statement of operations
Net loss from discontinued operations					$ (1,850,000)
Gain on sale of business, net of tax expense of $2,577					8,843,000
Tax expense					2,577,000
Net income from discontinued operations					6,993,000
EES Business | Disposed of by sale
Discontinued operations
Cash consideration received			$ 31,994,000
Gain on sale of business			11,420,000
Working capital dispute		$ 1,085,000
Amounts recorded in the consolidated financial statements		$ 0
Statement of operations
Net Sales					4,256,000
Cost of sales					4,278,000
Gross margin					(22,000)
Selling, general and administrative					1,453,000
Research and development					1,065,000
Other income, net					1,000
Loss from discontinued operations before income taxes					(2,539,000)
Benefit for income taxes					(689,000)
Net loss from discontinued operations					(1,850,000)
Gain on sale of business, net of tax expense of $2,577					8,843,000
Tax expense					2,577,000
Net income from discontinued operations					6,993,000
EES Business | Disposed of by sale | Other income (expense)
Statement of operations
Net Sales				$ 444,000	$ 399,000
Holdback | Disposed of by sale
Discontinued operations
Cash consideration received			$ 6,500,000
Number of remaining contracts | contract				2