Segment Information - Balance Sheet Information by Operating Segments (Detail) - USD ($) $ 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
Segment Reporting Information [Line Items]
non-compete agreements, net		$ 753					$ 828					$ 753		$ 828		$ 903		$ 978
customer relationships		2,839					664					2,839		664		715		766
goodwill		13,569					11,462					13,569		11,462		11,462		11,462
investment in unconsolidated joint venture		1,501					1,106					1,501		1,106
property, plant, and equipment		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
tradename		683										683
cash and cash equivalents		21,228					20,795					21,228		20,795		37,787		$ 29,725
short-term investments - available for sale		2,451					2,443					2,451		2,443
short-term investments - held-to-maturity		25,759										25,759
deferred income taxes		1,458					419					1,458		419
other current assets		2,870					2,894					2,870		2,894
long-term investments - held-to-maturity		5,035					30,945					5,035		30,945
long-term investments - rabbi trust		7,326					5,466					7,326		5,466
other assets		5,232					2,394					5,232		2,394
capital expenditures		1,568		1,274	1,529	3,068	3,097		6,590	5,541	3,543	7,439	[1]	18,771	[1]	10,708	[1]
Depreciation expense		1,992		$ 1,966	$ 1,905	$ 1,807	1,781		$ 1,793	$ 1,751	$ 1,761	7,672		7,085		6,671
Operating Segments [Member]
Segment Reporting Information [Line Items]
total assets		150,348					140,914					150,348		140,914		122,136
Operating Segments [Member] | Mattress Fabrics [Member]
Segment Reporting Information [Line Items]
current assets	[2]	43,935					47,038					43,935		47,038		43,472
non-compete agreements, net		753					828					753		828		903
customer relationships		613					664					613		664		715
goodwill		11,462					11,462					11,462		11,462		11,462
investment in unconsolidated joint venture		1,501					1,106					1,501		1,106
property, plant, and equipment		48,797	[3]				48,916	[4]				48,797	[3]	48,916	[4]	37,480	[5]
total assets		107,061					110,014					107,061		110,014		94,032
capital expenditures												6,713		17,689		9,666
Depreciation expense												6,850		6,245		5,837
Operating Segments [Member] | Upholstery Fabrics [Member]
Segment Reporting Information [Line Items]
current assets	[2]	35,826					29,021					35,826		29,021		26,540
customer relationships		2,226										2,226
goodwill		2,107										2,107
property, plant, and equipment		2,445	[6]				1,879	[7]				2,445	[6]	1,879	[7]	1,564	[8]
total assets		43,287					30,900					43,287		30,900		28,104
tradename		683										683
capital expenditures												488		822		626
Depreciation expense												822		840		834
Unallocated Corporate [Member]
Segment Reporting Information [Line Items]
property, plant, and equipment	[9]	552					856					552		856		929
cash and cash equivalents		21,228					20,795					21,228		20,795		37,787
short-term investments - available for sale		2,451					2,443					2,451		2,443		4,359
short-term investments - held-to-maturity		25,759										25,759
income taxes receivable																155
deferred income taxes		1,458					419					1,458		419		2,319
other current assets		2,870					2,894					2,870		2,894		2,477
long-term investments - held-to-maturity		5,035					30,945					5,035		30,945
long-term investments - rabbi trust		7,326					5,466					7,326		5,466		4,025
other assets		$ 957					$ 902					957		902		955
capital expenditures												$ 238		$ 260		$ 416

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

[2] Current assets represent accounts receivable and inventory.

[3] The $48.8 million at April 29, 2018, represents property, plant, and equipment located in the U.S. of $35.4 million and located in Canada of $13.4 million.

[4] The $48.9 million at April 30, 2017, represents property, plant, and equipment located in the U.S. of $34.0 million and located in Canada of $14.9 million.

[5] The $37.5 million at May 1, 2016, represents property, plant, and equipment located in the U.S. of $24.8 million and located in Canada of $12.7 million.

[6] The $2.4 million at April 29, 2018, represents property, plant, and equipment located in the U.S. of $1.8 million and located in China of $661.

[7] The $1.9 million at April 30, 2017, represents property, plant, and equipment located in the U.S. of $1.2 million and located in China of $655.

[8] The $1.6 million at May 1, 2016, represents property, plant, and equipment located in the U.S. of $893 and located in China of $671.

[9] The $552, $856, and $929 balance at April 29, 2018, April 30, 2017, and May 1, 2016, represent property, plant, and equipment associated with unallocated corporate departments and corporate departments shared by both the mattress and upholstery fabric segments located in the U.S.