Segment and Geographic Data - Information by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 28, 2018	Jan. 27, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jul. 30, 2016	Apr. 27, 2019	Apr. 28, 2018	Apr. 29, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 1,436,706	$ 1,396,745	$ 1,404,752	$ 1,336,320	$ 1,400,609	$ 1,375,222	$ 1,385,737	$ 1,304,115	$ 5,574,523	$ 5,465,683	$ 5,593,127
Property and equipment, net	290,590								305,790	290,590
Assets	3,471,664								3,269,269	3,471,664
Dental net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									2,191,790	2,196,078	2,390,219
Assets	853,555								641,721	853,555
Animal Health net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									3,354,528	3,242,564	3,159,826
Assets	2,128,800								2,156,723	2,128,800
Corporate net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									28,205	27,041	43,082
Assets	489,309								470,825	489,309
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									4,638,184	4,537,326	4,725,322
Property and equipment, net	278,508								295,381	278,508
United States | Dental net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									1,989,875	1,985,398	2,185,341
United States | Animal Health net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									2,620,104	2,524,887	2,496,899
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									597,953	583,057	547,968
Property and equipment, net	1,773								1,976	1,773
United Kingdom | Animal Health net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									597,953	583,057	547,968
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									338,386	345,300	319,837
Property and equipment, net	$ 10,309								8,433	10,309
Canada | Dental net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									201,915	210,680	204,878
Canada | Animal Health net sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									$ 136,471	$ 134,620	$ 114,959