Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Apr. 25, 2020 USD ($) Segment reporting_unit	Apr. 27, 2019 USD ($)	Apr. 28, 2018 USD ($)
Accounting Policies [Abstract]
Number of reportable segments | Segment	3
Maturity period of maximum (in days)	90 days
Inventories valued at LIFO as % of total inventories	83.00%	82.00%
Inventory, LIFO reserve	$ 99,726,000	$ 91,342,000
Property, Plant and Equipment [Line Items]
Number of reporting units | reporting_unit	2
Goodwill impairment	$ 675,055,000	0	$ 0
Contract assets	1,586,000	0
Contract liabilities	21,205,000	22,004,000
Contract liability, revenue recognized	$ 19,291,000
Liability for percentage of maximum potential amount that could be redeemed	92.00%
Advertising expense	$ 5,793,000	$ 8,356,000	$ 6,926,000
Building
Property, Plant and Equipment [Line Items]
Estimated useful lives	39 years
Computer Hardware And Software | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Computer Hardware And Software | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Office Furniture And Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Office Furniture And Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years