Warranty Reserves Estimated Cost (Details) - USD ($)	3 Months Ended	9 Months Ended
	Jan. 28, 2017	Jan. 28, 2017	Jan. 30, 2016	Jul. 30, 2016	Apr. 30, 2016	Jul. 31, 2015	Apr. 30, 2015
Standard Product Warranty Accrual, Preexisting, Increase (Decrease)	$ 200,000	$ 1,428,000	$ (424,000)
Standard Product Warranty Accrual	3,454,000	3,454,000	$ 2,862,000	$ 3,688,000	$ 4,134,000	$ 2,338,000	$ 2,653,000
UAS
Standard Product Warranty Accrual, Preexisting, Increase (Decrease)	328,000	1,735,000
Standard Product Warranty Accrual	$ 950,000	950,000
Product Warranty Expense		$ 1,329,000