Segment Reporting - Sales Information by Product (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 30, 2016	Jan. 24, 2015	Jan. 30, 2016	Jan. 24, 2015
Segment Reporting Information [Line Items]
Net sales	$ 1,400,853	$ 958,628	$ 3,932,933	$ 2,875,804
Consumables [Member]
Segment Reporting Information [Line Items]
Net sales	1,059,838	638,541	3,042,634	2,020,345
Equipment and Software [Member]
Segment Reporting Information [Line Items]
Net sales	248,779	235,847	610,071	596,650
Other [Member]
Segment Reporting Information [Line Items]
Net sales	$ 92,236	$ 84,240	$ 280,228	$ 258,809