Segment Reporting - Information about Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 25, 2020	Jan. 26, 2019	Jan. 25, 2020	Jan. 26, 2019	Apr. 27, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,456,155	$ 1,396,745	$ 4,203,550	$ 4,137,817
Operating income (loss)	43,816	45,363	42,344	91,093
Total assets	3,513,552		3,513,552		$ 3,269,269
Consumable
Segment Reporting Information [Line Items]
Net sales	1,091,571	1,079,566	3,315,759	3,327,214
Equipment and software
Segment Reporting Information [Line Items]
Net sales	270,325	234,251	612,167	563,269
Value-added services and other
Segment Reporting Information [Line Items]
Net sales	94,259	82,928	275,624	247,334
Dental
Segment Reporting Information [Line Items]
Net sales	626,589	579,733	1,692,328	1,628,313
Dental | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	48,822	51,120	135,458	128,587
Total assets	749,074		749,074		641,721
Dental | Consumable
Segment Reporting Information [Line Items]
Net sales	300,406	294,708	905,540	902,753
Dental | Equipment and software
Segment Reporting Information [Line Items]
Net sales	252,874	217,649	566,750	520,292
Dental | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	73,309	67,376	220,038	205,268
Animal Health
Segment Reporting Information [Line Items]
Net sales	817,285	807,495	2,483,012	2,488,117
Animal Health | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	13,438	15,033	51,236	56,096
Total assets	2,224,069		2,224,069		2,156,723
Animal Health | Consumable
Segment Reporting Information [Line Items]
Net sales	791,165	784,858	2,410,219	2,424,461
Animal Health | Equipment and software
Segment Reporting Information [Line Items]
Net sales	17,451	16,602	45,417	42,977
Animal Health | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	8,669	6,035	27,376	20,679
Corporate
Segment Reporting Information [Line Items]
Net sales	12,281	9,517	28,210	21,387
Corporate | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	(18,444)	(20,790)	(144,350)	(93,590)
Total assets	540,409		540,409		$ 470,825
Corporate | Value-added services and other
Segment Reporting Information [Line Items]
Net sales	12,281	9,517	28,210	21,387
United States
Segment Reporting Information [Line Items]
Net sales	1,217,291	1,170,446	3,491,053	3,440,533
United States | Dental
Segment Reporting Information [Line Items]
Net sales	570,639	529,522	1,528,422	1,478,552
United States | Animal Health
Segment Reporting Information [Line Items]
Net sales	634,371	631,407	1,934,421	1,940,594
United States | Corporate
Segment Reporting Information [Line Items]
Net sales	12,281	9,517	28,210	21,387
United Kingdom
Segment Reporting Information [Line Items]
Net sales	152,367	141,877	455,185	446,234
United Kingdom | Animal Health
Segment Reporting Information [Line Items]
Net sales	152,367	141,877	455,185	446,234
Canada
Segment Reporting Information [Line Items]
Net sales	86,497	84,422	257,312	251,050
Canada | Dental
Segment Reporting Information [Line Items]
Net sales	55,950	50,211	163,906	149,761
Canada | Animal Health
Segment Reporting Information [Line Items]
Net sales	$ 30,547	$ 34,211	$ 93,406	$ 101,289