Customer Financing (Detail)	3 Months Ended
	Jul. 28, 2018 USD ($) finance_agreement	Jul. 29, 2017 USD ($)	Apr. 28, 2018 USD ($)	Apr. 29, 2017 USD ($)
Customer Financing [Line Items]
Maximum credit financed for equipment purchases for any one customer	$ 1,000,000
Number of customer financing contracts | finance_agreement	2
Financing contracts sold under ASC 860	$ 47,310,000	$ 56,123,000
Revenues from Sale of Financing Contracts	2,491,000	4,260,000
Cash and cash equivalents	91,476,000	$ 99,779,000	$ 62,984,000	$ 94,959,000
Current receivables of finance contracts not yet sold	28,624,000			46,232,000
Unearned income	0			8,000
Finance contracts receivable sold and outstanding	580,977,000
Deferred purchase price	$ 106,412,000			150,404,000
Bad debt write-offs, percentage (less than)	1.00%
Unsettled Financing Arrangements
Customer Financing [Line Items]
Cash and cash equivalents	$ 37,328,000			$ 35,741,000
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