Segment Reporting - Information about Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 24, 2020	Oct. 26, 2019	Oct. 24, 2020	Oct. 26, 2019	Apr. 25, 2020
Segment Reporting Information [Line Items]
Net sales	$ 1,553,168	$ 1,418,744	$ 2,799,005	$ 2,747,395
Operating income (loss)	73,706	(18,146)	111,578	(1,472)
Total assets	2,789,024		2,789,024		$ 2,715,350
Consumable
Segment Reporting Information [Line Items]
Net sales	1,241,586	1,127,481	2,286,567	2,222,665
Equipment and software
Segment Reporting Information [Line Items]
Net sales	220,181	205,790	349,558	348,323
Value-added services and other
Segment Reporting Information [Line Items]
Net sales	91,401	85,473	162,880	176,407
Dental
Segment Reporting Information [Line Items]
Net sales	631,748	564,603	1,062,043	1,065,739
Dental | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	72,957	52,632	110,726	86,636
Total assets	790,788		790,788		704,216
Dental | Consumable
Segment Reporting Information [Line Items]
Net sales	357,849	304,565	614,452	608,039
Dental | Equipment and software
Segment Reporting Information [Line Items]
Net sales	198,135	188,192	311,098	313,876
Dental | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	75,764	71,846	136,493	143,824
Animal Health
Segment Reporting Information [Line Items]
Net sales	914,177	848,188	1,726,330	1,665,727
Animal Health | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	17,591	18,174	34,990	37,798
Total assets	1,445,853		1,445,853		1,485,284
Animal Health | Consumable
Segment Reporting Information [Line Items]
Net sales	883,737	822,916	1,672,115	1,614,626
Animal Health | Equipment and software
Segment Reporting Information [Line Items]
Net sales	22,046	17,598	38,460	34,447
Animal Health | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	8,394	7,674	15,755	16,654
Corporate
Segment Reporting Information [Line Items]
Net sales	7,243	5,953	10,632	15,929
Corporate | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	(16,842)	(88,952)	(34,138)	(125,906)
Total assets	552,383		552,383		$ 525,850
Corporate | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	7,243	5,953	10,632	15,929
United States
Segment Reporting Information [Line Items]
Net sales	1,279,106	1,183,047	2,313,978	2,273,762
United States | Dental
Segment Reporting Information [Line Items]
Net sales	570,769	513,141	968,229	957,783
United States | Animal Health
Segment Reporting Information [Line Items]
Net sales	701,094	663,953	1,335,117	1,300,050
United States | Corporate
Segment Reporting Information [Line Items]
Net sales	7,243	5,953	10,632	15,929
United Kingdom
Segment Reporting Information [Line Items]
Net sales	179,695	153,404	329,087	302,818
United Kingdom | Animal Health
Segment Reporting Information [Line Items]
Net sales	179,695	153,404	329,087	302,818
Canada
Segment Reporting Information [Line Items]
Net sales	94,367	82,293	155,940	170,815
Canada | Dental
Segment Reporting Information [Line Items]
Net sales	60,979	51,462	93,814	107,956
Canada | Animal Health
Segment Reporting Information [Line Items]
Net sales	$ 33,388	$ 30,831	$ 62,126	$ 62,859