Segment Information - International net sales (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
Revenues from External Customers and Long-Lived Assets [Line Items]
net sales		$ 78,184	$ 85,310	$ 80,698	$ 79,533	$ 77,350	$ 76,169	$ 75,343	$ 80,682	$ 323,725	$ 309,544	$ 312,860
North america (excluding USA) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
net sales	[1]									27,844	29,995	31,667
Far east and asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
net sales	[2]									40,671	34,695	31,927
All other areas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
net sales										5,681	3,618	4,336
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
net sales										$ 74,196	$ 68,308	$ 67,930

[1] Of this amount, $21.9 million, $22.3 million, and $24.2 million are attributable to shipments to Mexico in fiscal 2018, 2017, and 2016, respectively.

[2] Of this amount $32.6 million, $26.6 million, and $23.1 million are attributable to shipments to China in fiscal 2018, 2017, and 2016, respectively.