Segment Reporting - Information about Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jul. 28, 2018	Jul. 29, 2017	Apr. 28, 2018
Segment Reporting Information [Line Items]
Net sales	$ 1,336,320	$ 1,304,115
Operating income (loss)	4,514	56,833
Total assets	3,287,758		$ 3,471,664
Consumable
Segment Reporting Information [Line Items]
Net sales	1,109,397	1,080,105
Equipment and software
Segment Reporting Information [Line Items]
Net sales	146,898	136,949
Other
Segment Reporting Information [Line Items]
Net sales	80,025	87,061
Dental
Segment Reporting Information [Line Items]
Net sales	506,064	518,807
Dental | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	35,873	59,519
Total assets	693,540		853,555
Dental | Consumable
Segment Reporting Information [Line Items]
Net sales	304,239	320,178
Dental | Equipment and software
Segment Reporting Information [Line Items]
Net sales	134,957	127,863
Dental | Other
Segment Reporting Information [Line Items]
Net sales	66,868	70,766
Animal Health
Segment Reporting Information [Line Items]
Net sales	825,214	776,136
Animal Health | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	19,032	16,676
Total assets	2,163,953		2,128,800
Animal Health | Consumable
Segment Reporting Information [Line Items]
Net sales	805,158	759,927
Animal Health | Equipment and software
Segment Reporting Information [Line Items]
Net sales	11,941	9,086
Animal Health | Other
Segment Reporting Information [Line Items]
Net sales	8,115	7,123
Corporate
Segment Reporting Information [Line Items]
Net sales	5,042	9,172
Corporate | Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	(50,391)	(19,362)
Total assets	430,265		$ 489,309
Corporate | Other
Segment Reporting Information [Line Items]
Net sales	5,042	9,172
United States
Segment Reporting Information [Line Items]
Net sales	1,096,464	1,080,327
United States | Dental
Segment Reporting Information [Line Items]
Net sales	453,573	466,688
United States | Animal Health
Segment Reporting Information [Line Items]
Net sales	637,849	604,467
United States | Corporate
Segment Reporting Information [Line Items]
Net sales	5,042	9,172
United Kingdom
Segment Reporting Information [Line Items]
Net sales	153,905	140,854
United Kingdom | Dental
Segment Reporting Information [Line Items]
Net sales	0	0
United Kingdom | Animal Health
Segment Reporting Information [Line Items]
Net sales	153,905	140,854
United Kingdom | Corporate
Segment Reporting Information [Line Items]
Net sales	0	0
Canada
Segment Reporting Information [Line Items]
Net sales	85,951	82,934
Canada | Dental
Segment Reporting Information [Line Items]
Net sales	52,491	52,119
Canada | Animal Health
Segment Reporting Information [Line Items]
Net sales	33,460	30,815
Canada | Corporate
Segment Reporting Information [Line Items]
Net sales	$ 0	$ 0