Information about Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 26, 2013	Oct. 27, 2012	Oct. 26, 2013	Oct. 27, 2012
Segment Reporting Information [Line Items]
Net sales	$ 998,834	$ 867,193	$ 1,878,959	$ 1,756,418
Operating income	75,223	77,869	156,504	160,461
Dental Supply
Segment Reporting Information [Line Items]
Net sales	563,052	549,149	1,117,285	1,116,541
Operating income	53,174	50,750	108,664	106,621
Veterinary Supply
Segment Reporting Information [Line Items]
Net sales	308,120	184,375	507,803	375,465
Operating income	12,151	9,219	21,198	19,438
Rehabilitation Supply
Segment Reporting Information [Line Items]
Net sales	127,662	133,669	253,871	264,412
Operating income	$ 9,898	$ 17,900	$ 26,642	$ 34,402