Customer Financing (Details)	12 Months Ended
	Apr. 28, 2018 USD ($) contract	Apr. 29, 2017 USD ($)	Apr. 30, 2016 USD ($)	Apr. 25, 2015 USD ($)
Customer Financing [Line Items]
Maximum credit financed for equipment purchases for any one customer	$ 1,000,000
Number of customer financing contracts | contract	2
Financing contracts sold under ASC 860	$ 312,699,000	$ 357,965,000	$ 359,646,000
Net sales from sales of financing contracts	13,347,000	20,580,000	30,123,000
Cash and cash equivalents	62,984,000	94,959,000	$ 137,453,000	$ 347,260,000
Current receivables of finance contracts not yet sold	46,232,000	124,098,000
Unearned income	8,000	940,000
Finance contracts receivable sold and outstanding	617,610,000
Deferred purchase price receivable	$ 150,404,000	119,798,000
Maximum bad debt write-offs (percentage)	1.00%
Unsettled Financing Arrangements
Customer Financing [Line Items]
Cash and cash equivalents	$ 35,741,000	$ 17,902,000
The Bank of Tokyo-Mitsubishi UFJ, Ltd.
Customer Financing [Line Items]
Percentage of principal amount of financing contracts held as collateral (at least)	9.50%
Capacity under agreement	$ 575,000,000
Fifth Third Bank
Customer Financing [Line Items]
Percentage of principal amount of financing contracts held as collateral (at least)	11.00%
Capacity under agreement	$ 100,000,000