Segment Reporting - Information about Reportable Segments (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 29, 2016 USD ($)	Oct. 31, 2015 USD ($)	Oct. 29, 2016 USD ($) Segment	Oct. 31, 2015 USD ($)	Apr. 30, 2016 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment			3
Segment Reporting Information [Line Items]
Net sales	$ 1,418,241	$ 1,389,210	$ 2,750,677	$ 2,532,080
Operating income (loss) from continuing operations	79,803	83,463	145,219	145,640
Total assets	3,590,368		3,590,368		$ 3,520,804
Operating Segments [Member] | Dental [Member]
Segment Reporting Information [Line Items]
Net sales	601,553	601,322	1,156,568	1,176,439
Operating income (loss) from continuing operations	77,043	74,094	137,338	141,346
Total assets	930,541		930,541		994,113
Operating Segments [Member] | Animal Health [Member]
Segment Reporting Information [Line Items]
Net sales	807,146	774,453	1,569,777	1,331,750
Operating income (loss) from continuing operations	21,854	25,177	36,683	38,149
Total assets	2,148,059		2,148,059		2,064,302
Operating Segments [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Net sales	9,542	13,435	24,332	23,891
Operating income (loss) from continuing operations	(19,094)	$ (15,808)	(28,802)	$ (33,855)
Total assets	$ 511,768		$ 511,768		$ 462,389