Segment Reporting - Sales Information by Product (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 29, 2016	Oct. 31, 2015	Oct. 29, 2016	Oct. 31, 2015
Segment Reporting Information [Line Items]
Net sales	$ 1,418,241	$ 1,389,210	$ 2,750,677	$ 2,532,080
Consumable [Member]
Segment Reporting Information [Line Items]
Net sales	1,112,232	1,087,489	2,188,453	1,982,796
Equipment and Software [Member]
Segment Reporting Information [Line Items]
Net sales	217,194	207,809	378,140	361,292
Other [Member]
Segment Reporting Information [Line Items]
Net sales	$ 88,815	$ 93,912	$ 184,084	$ 187,992