Segment Information - International net sales (Parenthetical) (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
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
net sales									21,900	22,300	24,200
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
net sales									$ 32,600	$ 26,600	$ 23,100