Selected Quarterly Data (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Apr. 30, 2017	Jan. 29, 2017	Oct. 30, 2016	Jul. 31, 2016	May 01, 2016	Jan. 31, 2016	Nov. 01, 2015	Aug. 02, 2015	Apr. 30, 2017		May 01, 2016		May 03, 2015		Apr. 27, 2014
INCOME STATEMENT DATA
net sales		$ 77,350	$ 76,169	$ 75,343	$ 80,682	$ 77,253	$ 78,466	$ 76,956	$ 80,185	$ 309,544		$ 312,860		$ 310,166
cost of sales		60,194	59,410	58,442	62,263	60,640	61,903	61,223	63,983	240,309		247,749		254,599
gross profit		17,156	16,759	16,901	18,419	16,613	16,563	15,733	16,202	69,235		65,111		55,567
selling, general and administrative expenses		9,986	9,824	9,602	9,746	9,261	9,337	9,433	8,741	39,157		36,773		32,778
income from operations		7,170	6,935	7,299	8,673	7,352	7,226	6,300	7,461	30,078		28,338		22,789
interest expense									24					64
interest income		(134)	(124)	(15)	(25)	(26)	(38)	(69)	(66)	(299)		(176)		(622)
other expense		305	69	155	152	211	85	225	95	681		616		391
income before income taxes		6,999	6,990	7,159	8,546	7,167	7,179	6,144	7,408	29,696		27,898		22,956
income taxes		778	643	2,684	3,233	3,566	2,317	2,373	2,707	7,339		10,963		7,885
loss from investment in unconsolidated joint venture		23								23
net income		6,198	6,347	4,475	5,313	3,601	4,862	3,771	4,701	22,334		16,935		15,071
depreciation		$ 1,781	$ 1,793	$ 1,751	$ 1,761	$ 1,783	$ 1,705	$ 1,629	$ 1,555	$ 7,085		$ 6,671		$ 5,773
weighted average shares outstanding		12,340,000	12,313,000	12,308,000	12,286,000	12,257,000	12,331,000	12,343,000	12,277,000	12,312,000		12,302,000		12,217,000
weighted average shares outstanding, assuming dilution		12,567,000	12,544,000	12,507,000	12,463,000	12,434,000	12,486,000	12,484,000	12,456,000	12,518,000		12,475,000		12,422,000
PER SHARE DATA
net income per share - basic		$ 0.50	$ 0.52	$ 0.36	$ 0.43	$ 0.29	$ 0.39	$ 0.31	$ 0.38	$ 1.81		$ 1.38		$ 1.23
net income per share - diluted		0.49	0.51	0.36	0.43	0.29	0.39	0.30	0.38	$ 1.78		$ 1.36		$ 1.21
dividends per share		0.08	0.08	0.07	0.28	0.07	0.07	0.06	0.46
book value		$ 12.03	$ 11.56	$ 11.04	$ 10.68	$ 10.50	$ 10.21	$ 9.96	$ 9.62
BALANCE SHEET DATA
operating working capital	[1]	$ 40,869	$ 40,973	$ 41,810	$ 43,486	$ 45,794	$ 49,288	$ 43,303	$ 43,405	$ 40,869		$ 45,794
property, plant and equipment, net		51,651	50,333	45,537	41,745	39,973	38,157	38,319	37,480	51,651		39,973
total assets		205,634	191,056	179,127	183,360	175,142	173,551	168,947	166,880	205,634		175,142		$ 171,300
capital expenditures		3,097	6,590	5,541	3,543	3,631	1,542	2,575	2,960	18,771	[2]	10,708	[2]	11,174	[2]
dividends paid		988	985	862	3,445	859	864	741	5,676	6,280		8,140		7,579
long-term debt, current maturities of long-term debt, and line of credit	[3]				7,000				2,200
shareholders' equity		148,630	142,314	135,949	131,435	128,812	125,074	122,975	118,725	148,630		128,812		$ 119,427		$ 111,744
capital employed	[4]	$ 98,429	$ 97,788	$ 94,101	$ 94,599	$ 90,357	$ 90,983	$ 88,297	$ 90,593	$ 98,429		$ 90,357
RATIOS & OTHER DATA
gross profit margin		22.20%	22.00%	22.40%	22.80%	21.50%	21.10%	20.40%	20.20%
operating income margin		9.30%	9.10%	9.70%	10.70%	9.50%	9.20%	8.20%	9.30%
net income margin		8.00%	8.30%	5.90%	6.60%	4.70%	6.20%	4.90%	5.90%
effective income tax rate		11.10%	9.20%	37.50%	37.80%	49.80%	32.30%	38.60%	36.50%	24.70%		39.30%		34.30%
Debt-to-total capital employed ratio	[3]	0.00%	0.00%	0.00%	7.40%	0.00%	0.00%	0.00%	2.40%	0.00%		0.00%
operating working capital turnover	[1]	730.00%	700.00%	700.00%	700.00%	700.00%	720.00%	770.00%	770.00%
days sales in receivables		29 days	27 days	23 days	26 days	28 days	31 days	28 days	29 days
inventory turnover		500.00%	520.00%	520.00%	530.00%	530.00%	510.00%	530.00%	560.00%
stock price
high		$ 34.50	$ 37.80	$ 34.30	$ 30.11	$ 28.53	$ 31.15	$ 35.23	$ 33.64
low		30.25	26.80	26.72	25.57	22.72	22.61	29.13	25.22
close		$ 32.10	$ 33.80	$ 28.15	$ 28.53	$ 26.24	$ 25.32	$ 30.01	$ 30.25	$ 32.10		$ 26.24
daily average trading volume (shares)		37.7	43.5	45.9	40.9	33.5	68.8	76.2	90.5

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

[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 includes long-term debt, current maturities of long-term debt, and line of credit.

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