Customer Financing (Details)	12 Months Ended
	Apr. 29, 2017 USD ($) contract	Apr. 30, 2016 USD ($)	Apr. 25, 2015 USD ($)	Apr. 26, 2014 USD ($)
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	$ 357,965,000	$ 359,646,000	$ 312,303,000
Net sales from sales of financing contracts	20,580,000	30,123,000	21,668,000
Cash and cash equivalents	94,959,000	137,453,000	$ 347,260,000	$ 264,908,000
Current receivables of finance contracts not yet sold	124,098,000	87,406,000
Unearned income	940,000	1,768,000
Finance contracts receivable sold and outstanding	613,586,000
Deferred purchase price receivable	$ 119,798,000	108,837,000
Maximum bad debt write-offs (percentage)	1.00%
Unsettled Financing Arrangements [Member]
Customer Financing [Line Items]
Cash and cash equivalents	$ 17,902,000	$ 27,186,000
The Bank of Tokyo-Mitsubishi UFJ, Ltd. [Member]
Customer Financing [Line Items]
Percentage of principal amount of financing contracts held as collateral (at least)	9.00%
Capacity under agreement	$ 575,000,000
Fifth Third Bank [Member]
Customer Financing [Line Items]
Percentage of principal amount of financing contracts held as collateral (at least)	10.00%
Capacity under agreement	$ 100,000,000