Sales Information by Product (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 26, 2013	Jan. 28, 2012	Jan. 26, 2013	Jan. 28, 2012
Segment Reporting Information [Line Items]
Net sales	$ 915,861	$ 895,030	$ 2,672,279	$ 2,599,327
Consumable and printed products
Segment Reporting Information [Line Items]
Net sales	551,150	550,888	1,725,465	1,695,822
Equipment and software
Segment Reporting Information [Line Items]
Net sales	292,725	273,573	726,687	687,249
Other
Segment Reporting Information [Line Items]
Net sales	$ 71,986	$ 70,569	$ 220,127	$ 216,256