Segment and Geographic Data - Information about Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Apr. 26, 2014	Jan. 25, 2014	Oct. 26, 2013	Jul. 27, 2013	Apr. 27, 2013	Jan. 26, 2013	Oct. 27, 2012	Jul. 28, 2012	Apr. 26, 2014	Apr. 27, 2013	Apr. 28, 2012
Segment Reporting Information [Line Items]
Net sales	$ 1,102,077	$ 1,082,679	$ 998,834	$ 880,125	$ 964,933	$ 915,861	$ 867,193	$ 889,225	$ 4,063,715	$ 3,637,212	$ 3,535,661
Operating income	92,601	96,651	75,223	81,281	104,456	89,538	77,869	82,592	345,756	354,455	358,009
Depreciation and amortization									49,986	46,002	42,209
Total assets	2,864,677				2,681,778				2,864,677	2,681,778	2,739,368
Dental supply [Member]
Segment Reporting Information [Line Items]
Net sales									2,382,096	2,379,970	2,287,875
Operating income									249,138	247,747	246,755
Depreciation and amortization									35,209	34,953	31,375
Total assets	1,342,333				1,442,667				1,342,333	1,442,667	1,502,672
Rehabilitation supply [Member]
Segment Reporting Information [Line Items]
Net sales									478,574	501,997	513,340
Operating income									46,763	65,027	72,442
Depreciation and amortization									7,540	7,683	7,472
Total assets	876,211				881,323				876,211	881,323	883,287
Veterinary supply [Member]
Segment Reporting Information [Line Items]
Net sales									1,203,045	755,245	734,446
Operating income									49,855	41,681	38,812
Depreciation and amortization									7,237	3,366	3,362
Total assets	$ 646,133				$ 357,788				$ 646,133	$ 357,788	$ 353,409