Segment Reporting - Information about Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 26, 2019	Oct. 27, 2018	Oct. 26, 2019	Oct. 27, 2018	Apr. 27, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,418,744	$ 1,404,752	$ 2,747,395	$ 2,741,072
Operating income (loss)	(18,146)	41,216	(1,472)	45,730
Total assets	3,435,457		3,435,457		$ 3,269,269
Consumable
Segment Reporting Information [Line Items]
Net sales	1,128,171	1,138,251	2,224,188	2,247,648
Equipment and software
Segment Reporting Information [Line Items]
Net sales	202,605	182,120	341,842	329,018
Value-added services and other
Segment Reporting Information [Line Items]
Net sales	87,968	84,381	181,365	164,406
Dental
Segment Reporting Information [Line Items]
Net sales	564,603	542,516	1,065,739	1,048,580
Dental | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	52,632	41,594	86,636	77,467
Total assets	714,914		714,914		641,721
Dental | Consumable
Segment Reporting Information [Line Items]
Net sales	303,123	303,806	605,134	608,045
Dental | Equipment and software
Segment Reporting Information [Line Items]
Net sales	188,192	167,686	313,876	302,643
Dental | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	73,288	71,024	146,729	137,892
Animal Health
Segment Reporting Information [Line Items]
Net sales	848,188	855,408	1,665,727	1,680,622
Animal Health | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	18,174	22,031	37,798	41,063
Total assets	2,255,741		2,255,741		2,156,723
Animal Health | Consumable
Segment Reporting Information [Line Items]
Net sales	825,048	834,445	1,619,054	1,639,603
Animal Health | Equipment and software
Segment Reporting Information [Line Items]
Net sales	14,413	14,434	27,966	26,375
Animal Health | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	8,727	6,529	18,707	14,644
Corporate
Segment Reporting Information [Line Items]
Net sales	5,953	6,828	15,929	11,870
Corporate | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	(88,952)	(22,409)	(125,906)	(72,800)
Total assets	464,802		464,802		$ 470,825
Corporate | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	5,953	6,828	15,929	11,870
United States
Segment Reporting Information [Line Items]
Net sales	1,183,047	1,173,623	2,273,762	2,270,087
United States | Dental
Segment Reporting Information [Line Items]
Net sales	513,141	495,457	957,783	949,030
United States | Animal Health
Segment Reporting Information [Line Items]
Net sales	663,953	671,338	1,300,050	1,309,187
United States | Corporate
Segment Reporting Information [Line Items]
Net sales	5,953	6,828	15,929	11,870
United Kingdom
Segment Reporting Information [Line Items]
Net sales	153,404	150,452	302,818	304,357
United Kingdom | Animal Health
Segment Reporting Information [Line Items]
Net sales	153,404	150,452	302,818	304,357
Canada
Segment Reporting Information [Line Items]
Net sales	82,293	80,677	170,815	166,628
Canada | Dental
Segment Reporting Information [Line Items]
Net sales	51,462	47,059	107,956	99,550
Canada | Animal Health
Segment Reporting Information [Line Items]
Net sales	$ 30,831	$ 33,618	$ 62,859	$ 67,078