Segment Reporting - Information about Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jul. 29, 2017	Jul. 30, 2016	Apr. 29, 2017
Segment Reporting Information [Line Items]
Net sales	$ 1,304,115	$ 1,332,436
Operating income (loss)	56,833	65,416
Total assets	3,495,242		$ 3,507,913
Operating Segments | Dental
Segment Reporting Information [Line Items]
Net sales	518,807	555,015
Operating income (loss)	59,519	60,295
Total assets	874,097		863,970
Operating Segments | Animal Health
Segment Reporting Information [Line Items]
Net sales	776,136	762,631
Operating income (loss)	16,676	14,829
Total assets	2,148,244		2,119,512
Operating Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	9,172	14,790
Operating income (loss)	(19,362)	$ (9,708)
Total assets	$ 472,901		$ 524,431