Segment Reporting - Information about Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 28, 2017	Oct. 29, 2016	Oct. 28, 2017	Oct. 29, 2016	Apr. 29, 2017
Segment Reporting Information [Line Items]
Net sales	$ 1,385,737	$ 1,418,241	$ 2,689,852	$ 2,750,677
Operating income (loss)	71,759	79,803	128,592	145,219
Total assets	3,528,479		3,528,479		$ 3,507,913
Operating Segments | Dental
Segment Reporting Information [Line Items]
Net sales	553,630	601,553	1,072,437	1,156,568
Operating income (loss)	65,207	77,043	124,726	137,338
Total assets	903,155		903,155		863,970
Operating Segments | Animal Health
Segment Reporting Information [Line Items]
Net sales	823,583	807,146	1,599,719	1,569,777
Operating income (loss)	23,217	21,854	39,893	36,683
Total assets	2,171,844		2,171,844		2,119,512
Operating Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	8,524	9,542	17,696	24,332
Operating income (loss)	(16,665)	$ (19,094)	(36,027)	$ (28,802)
Total assets	$ 453,480		$ 453,480		$ 524,431