Selected Quarterly Data (Unaudited) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Apr. 28, 2013		Jan. 27, 2013		Oct. 28, 2012		Jul. 29, 2012		Apr. 29, 2012		Jan. 29, 2012		Oct. 30, 2011		Jul. 31, 2011		Apr. 28, 2013		Apr. 29, 2012		May 01, 2011	May 02, 2010
INCOME STATEMENT DATA
net sales	$ 70,375		$ 63,695		$ 65,560		$ 69,184		$ 75,711		$ 60,450		$ 58,013		$ 60,270		$ 268,814		$ 254,443		$ 216,806
cost of sales	57,527		52,010		53,683		56,064		62,013		51,939		49,367		51,392		219,284		214,711		179,966
gross profit	12,848		11,685		11,877		13,120		13,698		8,511		8,646		8,878		49,530		39,732		36,840
selling, general and administrative expenses	6,772		6,822		7,209		7,641		8,031		5,518		5,720		5,757		28,445		25,026		21,069
Income from operations	6,076		4,863		4,668		5,479		5,667		2,993		2,926		3,121		21,085		14,706		15,743
interest expense	140		145		156		190		190		181		188		220		632		780		881
interest income	(90)		(105)		(96)		(127)		(121)		(148)		(110)		(129)		(419)		(508)		(240)
other expense (income)	163		300		76		44		104		83		(15)		65		583		236		40
income before income taxes	5,863		4,523		4,532		5,372		5,494		2,877		2,863		2,965		20,289		14,198		15,062
income taxes	2,161		1,700		(3,736)		1,848		2,071		1,075		(3,389)		1,145		1,972		902		(1,102)
net income	3,702		2,823		8,268		3,524		3,423		1,802		6,252		1,820		18,317		13,296		16,164
depreciation	1,297		1,279		1,285		1,254		1,264		1,214		1,200		1,187		5,115		4,865		4,372
weighted average shares outstanding	12,102,000		12,095,000		12,191,000		12,551,000		12,513,000		12,536,000		12,733,000		13,061,000		12,235,000		12,711,000		12,959,000
weighted average shares outstanding, assuming dilution	12,323,000		12,290,000		12,348,000		12,711,000		12,695,000		12,677,000		12,871,000		13,205,000		12,450,000		12,866,000		13,218,000
PER SHARE DATA
net income per share - basic	$ 0.31		$ 0.23		$ 0.68		$ 0.28		$ 0.27		$ 0.14		$ 0.49		$ 0.14		$ 1.50		$ 1.05		$ 1.25
net income per share - diluted	$ 0.30		$ 0.23		$ 0.67		$ 0.28		$ 0.27		$ 0.14		$ 0.49		$ 0.14		$ 1.47		$ 1.03		$ 1.22
book value	$ 7.82		$ 7.52		$ 7.81		$ 7.26		$ 7.00		$ 6.73		$ 6.59		$ 6.17
BALANCE SHEET DATA
operating working capital	39,228	[1]	40,214	[1]	35,616	[1]	36,637	[1]	30,596	[1]	31,418	[1]	28,216	[1]	28,399	[1]	39,228	[1]	30,596	[1]
property, plant and equipment, net	30,594		30,055		30,621		31,016		31,279		30,285		30,431		30,615		30,594		31,279
total assets	144,706		143,797		142,443		143,160		144,716		131,457		127,124		129,307		144,706		144,716		130,051
capital expenditures	1,863		713		890		991		2,326		1,068		1,019		1,506		4,400		5,890		6,352
long-term debt, current maturities of long-term debt, and line of credit	7,161	[2]	7,342	[2]	7,692	[2]	9,900	[2]	10,012	[2]	9,166	[2]	9,219	[2]	11,488	[2]	7,161	[2]	10,012	[2]
shareholders' equity	95,583		91,966		95,388		91,831		89,000		85,371		84,097		81,351		95,583		89,000		80,341	63,047
capital employed	$ 72,699	[3]	$ 71,758	[3]	$ 70,596	[3]	$ 75,177	[3]	$ 67,887	[3]	$ 70,042	[3]	$ 66,889	[3]	$ 69,520	[3]	$ 72,699	[3]	$ 67,887	[3]
RATIOS & OTHER DATA
gross profit margin	18.30%		18.30%		18.10%		19.00%		18.10%		14.10%		14.90%		14.70%
operating income margin	8.60%		7.60%		7.10%		7.90%		7.50%		5.00%		5.00%		5.20%
net income margin	5.30%		4.40%		12.60%		5.10%		4.50%		3.00%		10.80%		3.00%
effective income tax rate	36.90%		37.60%		(82.40%)		34.40%		37.70%		37.40%		(118.40%)		38.60%		9.70%		6.40%		(7.30%)
Debt-to-total capital employed ratio	9.90%	[2]	10.20%	[2]	10.90%	[2]	13.20%	[2]	14.70%	[2]	13.10%	[2]	13.80%	[2]	16.50%	[2]	9.90%	[2]	14.70%	[2]
operating working capital turnover	7.4	[1]	7.9	[1]	8.3	[1]	8.5	[1]	8.9	[1]	8.7	[1]	8.7	[1]	8.6	[1]
days sales in receivables	30 days		32 days		29 days		24 days		29 days		31 days		25 days		26 days
inventory turnover	6.0		5.3		5.5		5.2		7.5		6.2		6.0		6.0
stock price
high	$ 18.15		$ 16.82		$ 12.35		$ 11.99		$ 11.81		$ 9.18		$ 9.75		$ 10.78
low	$ 14.76		$ 12.00		$ 9.75		$ 9.00		$ 8.90		$ 7.67		$ 7.05		$ 7.30
close	$ 16.25		$ 16.70		$ 12.28		$ 10.15		$ 11.05		$ 9.10		$ 8.65		$ 8.92		$ 16.25		$ 11.05
daily average trading volume (shares)	51.9		43.4		29.9		38.6		12.1		10.2		26.7		72.6

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

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

[3] Capital employed represents long-term and current maturities of long-term debt, lines of credit, current and noncurrent deferred income tax liabilities, current and long-term income taxes payable, stockholders' equity, offset by cash and cash equivalents, short-term investments, current and noncurrent deferred income tax assets, and income taxes receivable.