General and Summary of Significant Accounting Policies (Detail)	3 Months Ended								12 Months Ended
	Apr. 29, 2018 USD ($)	Jan. 28, 2018 USD ($)	Oct. 29, 2017 USD ($)	Jul. 30, 2017 USD ($)	Apr. 30, 2017 USD ($)	Jan. 29, 2017 USD ($)	Oct. 30, 2016 USD ($)	Jul. 31, 2016 USD ($)	Apr. 28, 2019	Apr. 29, 2018 USD ($) Segment	Apr. 30, 2017 USD ($)	May 01, 2016 USD ($)	Jan. 01, 2017
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of business segments | Segment										2
Short-term investments	$ 2,451,000				$ 2,443,000					$ 2,451,000	$ 2,443,000
long-term investments - rabbi trust	7,326,000				5,466,000					7,326,000	5,466,000
purchase of long-term investments (held-to-maturity)							$ 31,000,000				31,020,000
Amortized cost of held-to-maturity investments	30,800,000				30,900,000					30,800,000	30,900,000
Fair value of held-to-maturity investments	30,600,000				30,800,000					$ 30,600,000	30,800,000
Inventory aging categories										Inventory aging categories are six, nine, twelve, and fifteen months
Interest costs incurred on long-term debt and lines of credit										$ 194,000	158,000	$ 58,000
Interest cost capitalized										100,000	158,000	58,000
Income taxes	(6,217,000)	$ 8,208,000	$ 2,108,000	$ 1,640,000	778,000	$ 643,000	$ 2,684,000	$ 3,233,000		5,740,000	7,339,000	10,963,000
Net cash provided by operating activities										27,473,000	34,067,000	28,383,000
Net cash provided by financing activities										(12,012,000)	(7,724,000)	(13,418,000)
ASU No. 2016-09 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Income taxes										(497,000)
Selling, General and Administrative Expenses [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Handling costs										4,600,000	4,600,000	4,200,000
Scenario, Forecast [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Dividends received deduction percentage for earnings and profits received from foreign corporation									100.00%
Dividends received deduction, foreign corporation ownership percentage									10.00%
Short-term Investments [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Unrealized gain (loss) on investments	(91,000)				(47,000)					(91,000)	(47,000)
Long-term Investments (Rabbi Trust) [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Unrealized gain (loss) on investments	$ 61,000				$ 43,000					$ 61,000	43,000
Excess Tax Benefits from Stock Based Compensation Expense [Member] | ASU No. 2016-09 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Net cash provided by operating activities											657,000	841,000
Net cash provided by financing activities											(657,000)	(841,000)
Common Stock Shares Withheld to Satisfy Statutory Income Tax Withholding Obligation [Member] | ASU No. 2016-09 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Net cash provided by operating activities											429,000	747,000
Net cash provided by financing activities											$ (429,000)	$ (747,000)
Maximum [Member] | Investments (Held-To-Maturity) [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Investment maturity period										2 years 6 months
Minimum [Member] | Investments (Held-To-Maturity) [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Investment maturity period										2 years
CLIH [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%									50.00%			50.00%