Selected Quarterly Data (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Apr. 29, 2018	Jan. 28, 2018	Oct. 29, 2017	Jul. 30, 2017	Apr. 30, 2017	Jan. 29, 2017	Oct. 30, 2016	Jul. 31, 2016	Apr. 29, 2018		Apr. 30, 2017		May 01, 2016		May 03, 2015
INCOME STATEMENT DATA
net sales		$ 78,184	$ 85,310	$ 80,698	$ 79,533	$ 77,350	$ 76,169	$ 75,343	$ 80,682	$ 323,725		$ 309,544		$ 312,860
cost of sales		63,424	67,707	64,894	63,068	60,194	59,410	58,442	62,263	259,092		240,309		247,749
gross profit		14,760	17,603	15,804	16,465	17,156	16,759	16,901	18,419	64,633		69,235		65,111
selling, general and administrative expenses		8,296	9,959	9,415	9,501	9,986	9,824	9,602	9,746	37,172		39,157		36,773
income from operations		6,464	7,644	6,389	6,964	7,170	6,935	7,299	8,673	27,461		30,078		28,338
interest expense		26	31	37						94
interest income		(143)	(132)	(128)	(131)	(134)	(124)	(15)	(25)	(534)		(299)		(176)
other expense		115	229	321	353	305	69	155	152	1,018		681		616
income before income taxes		6,466	7,516	6,159	6,742	6,999	6,990	7,159	8,546	26,883		29,696		27,898
Income taxes		(6,217)	8,208	2,108	1,640	778	643	2,684	3,233	5,740		7,339		10,963
loss from investment in unconsolidated joint venture		17	56	75	118	23				266		23
net income (loss)		12,666	(748)	3,976	4,984	6,198	6,347	4,475	5,313	20,877		22,334		16,935
depreciation		$ 1,992	$ 1,966	$ 1,905	$ 1,807	$ 1,781	$ 1,793	$ 1,751	$ 1,761	$ 7,672		$ 7,085		$ 6,671
weighted average shares outstanding		12,450,000	12,436,000	12,440,000	12,399,000	12,340,000	12,313,000	12,308,000	12,286,000	12,431,000		12,312,000		12,302,000
weighted average shares outstanding, assuming dilution		12,611,000	12,436,000	12,580,000	12,590,000	12,567,000	12,544,000	12,507,000	12,463,000	12,633,000		12,518,000		12,475,000
PER SHARE DATA
net income (loss) per share - basic		$ 1.02	$ (0.06)	$ 0.32	$ 0.40	$ 0.50	$ 0.52	$ 0.36	$ 0.43	$ 1.68		$ 1.81		$ 1.38
net income (loss) per share - diluted		1.00	(0.06)	0.32	0.40	0.49	0.51	0.36	0.43	$ 1.65		$ 1.78		$ 1.36
dividends per share		0.09	0.09	0.08	0.29	0.08	0.08	0.07	0.28
book value		$ 13.12	$ 12.22	$ 12.31	$ 12.03	$ 12.03	$ 11.56	$ 11.04	$ 10.68
BALANCE SHEET DATA
operating working capital	[1]	$ 49,939	$ 47,760	$ 46,620	$ 42,608	$ 40,869	$ 40,973	$ 41,810	$ 43,486	$ 49,939		$ 40,869
property, plant and equipment, net		51,794	51,838	52,530	52,912	51,651	50,333	45,537	41,745	51,794		51,651
total assets		217,984	216,844	201,043	207,904	205,634	191,056	179,127	183,360	217,984		205,634		$ 175,142
capital expenditures		1,568	1,274	1,529	3,068	3,097	6,590	5,541	3,543	7,439	[2]	18,771	[2]	10,708	[2]
dividends paid		1,121	1,119	995	3,608	988	985	862	3,445	6,843		6,280		8,140
line of credit	[3]				5,000				7,000
shareholders' equity		163,376	152,182	153,080	149,677	148,630	142,314	135,949	131,435	163,376		148,630		$ 128,812		$ 119,427
capital employed	[4]	$ 114,817	$ 109,165	$ 109,373	$ 108,222	$ 98,429	$ 97,788	$ 94,101	$ 94,599	$ 114,817		$ 98,429
RATIOS & OTHER DATA
gross profit margin		18.90%	20.60%	19.60%	20.70%	22.20%	22.00%	22.40%	22.80%
operating income margin		8.30%	9.00%	7.90%	8.80%	9.30%	9.10%	9.70%	10.70%
net income margin		16.20%	(0.90%)	4.90%	6.30%	8.00%	8.30%	5.90%	6.60%
effective income tax rate		(96.10%)	109.20%	34.20%	24.30%	11.10%	9.20%	37.50%	37.80%	21.40%		24.70%		39.30%
Debt-to-total capital employed ratio	[3]	0.00%	0.00%	0.00%	4.60%	0.00%	0.00%	0.00%	7.40%	0.00%		0.00%
operating working capital turnover	[1]	710.00%	740.00%	740.00%	740.00%	730.00%	700.00%	700.00%	700.00%
days sales in receivables		30 days	28 days	27 days	25 days	29 days	27 days	23 days	26 days
inventory turnover		480.00%	520.00%	520.00%	470.00%	500.00%	520.00%	520.00%	530.00%
stock price
high		$ 32.29	$ 34.05	$ 33.25	$ 34.00	$ 34.50	$ 37.80	$ 34.30	$ 30.11
low		27.40	26.15	27.00	30.60	30.25	26.80	26.72	25.57
close		$ 30.10	$ 31.35	$ 31.95	$ 30.65	$ 32.10	$ 33.80	$ 28.15	$ 28.53	$ 30.10		$ 32.10
daily average trading volume (shares)		18.3	17.4	24.4	27.9	37.7	43.5	45.9	40.9

[1] Operating working capital for this calculation is accounts receivable and inventories, offset by accounts payable-trade, accounts payable - capital expenditures, and deferred revenue.

[2] Capital expenditure amounts are stated on an accrual basis. See Consolidated Statement of Cash Flows for capital expenditure amounts on a cash basis.

[3] Debt represents outstanding borrowings on our lines of credit.

[4] Capital employed does not include cash and cash equivalents, short-term investments (available-for-sale), short-term investments (held-to-maturity), long-term investments (held-to-maturity), long-term investments (rabbi trust), lines of credit, noncurrent deferred tax assets and liabilities, income taxes receivable and payable, and deferred compensation.