Segment Reporting - Sales Information by Product (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 28, 2017	Oct. 29, 2016	Oct. 28, 2017	Oct. 29, 2016
Segment Reporting Information [Line Items]
Net sales	$ 1,385,737	$ 1,418,241	$ 2,689,852	$ 2,750,677
Consumable
Segment Reporting Information [Line Items]
Net sales	1,116,091	1,112,232	2,196,196	2,188,453
Equipment and software
Segment Reporting Information [Line Items]
Net sales	181,337	217,194	318,286	378,140
Other
Segment Reporting Information [Line Items]
Net sales	$ 88,309	$ 88,815	$ 175,370	$ 184,084