Customer Financing (Detail)	3 Months Ended		6 Months Ended
	Oct. 26, 2019 USD ($)	Oct. 27, 2018 USD ($)	Oct. 26, 2019 USD ($) finance_agreement	Oct. 27, 2018 USD ($)	Apr. 27, 2019 USD ($)	Apr. 28, 2018 USD ($)
Customer Financing [Line Items]
Maximum credit financed for equipment purchases for any one customer	$ 1,000,000		$ 1,000,000
Number of customer financing contracts | finance_agreement			2
Financing contracts sold under ASC 860	35,321,000	$ 40,713,000	$ 101,624,000	$ 88,023,000
Revenues from Sale of Financing Contracts	3,550,000	2,734,000	10,896,000	5,225,000
Cash and cash equivalents	129,575,000	$ 165,515,000	129,575,000	$ 165,515,000	$ 95,646,000	$ 62,984,000
Current receivables of finance contracts not yet sold	52,042,000		52,042,000		48,559,000
Finance contracts receivable sold and outstanding	519,760,000		519,760,000
Deferred purchase price	102,083,000		$ 102,083,000		121,657,000
Bad debt write-offs, percentage (less than)			1.00%
Unsettled Financing Arrangements
Customer Financing [Line Items]
Cash and cash equivalents	35,947,000		$ 35,947,000		$ 34,016,000
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	525,000,000		$ 525,000,000
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		$ 100,000,000