Segment Reporting - Information about Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		9 Months Ended
	Jan. 27, 2018	Oct. 28, 2017	Jan. 28, 2017	Oct. 29, 2016	Oct. 28, 2017	Oct. 29, 2016	Jan. 27, 2018	Jan. 28, 2017	Apr. 29, 2017
Segment Reporting Information [Line Items]
Net sales	$ 1,375,222	$ 1,375,222	$ 1,397,418	$ 1,397,418	$ 4,065,074	$ 4,148,095	$ 4,065,074	$ 4,148,095
Operating income (loss) from continuing operations	50,046		46,554				178,638	191,773
Total assets	3,674,358						3,674,358		$ 3,507,913
Operating Segments | Dental
Segment Reporting Information [Line Items]
Net sales	577,877		626,343				1,650,314	1,782,911
Operating income (loss) from continuing operations	58,439		40,018				183,165	177,356
Total assets	953,273						953,273		863,970
Operating Segments | Animal Health
Segment Reporting Information [Line Items]
Net sales	794,867		762,577				2,394,586	2,332,354
Operating income (loss) from continuing operations	18,037		23,777				57,930	60,460
Total assets	2,196,733						2,196,733		2,119,512
Operating Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	2,478		8,498				20,174	32,830
Operating income (loss) from continuing operations	(26,430)		$ (17,241)				(62,457)	$ (46,043)
Total assets	$ 524,352						$ 524,352		$ 524,431