Segment and Geographic Data - Information about Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 28, 2018	Jan. 27, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jul. 30, 2016	Apr. 27, 2019	Apr. 28, 2018	Apr. 29, 2017
Segment Reporting Information [Line Items]
Operating income (loss) from continuing operations	$ 46,623	$ 45,363	$ 41,216	$ 4,514	$ 41,251	$ 50,046	$ 71,759	$ 56,833	$ 137,716	$ 219,889	$ 287,928
Depreciation and amortization									82,773	83,816	83,818
Total assets	3,471,664								3,269,269	3,471,664
Dental net sales
Segment Reporting Information [Line Items]
Operating income (loss) from continuing operations									179,236	229,201	263,671
Depreciation and amortization									8,792	7,435	11,840
Total assets	853,555								641,721	853,555
Animal Health net sales
Segment Reporting Information [Line Items]
Operating income (loss) from continuing operations									81,472	78,058	88,132
Depreciation and amortization									49,362	50,892	50,144
Total assets	2,128,800								2,156,723	2,128,800
Corporate net sales
Segment Reporting Information [Line Items]
Operating income (loss) from continuing operations									(122,992)	(87,370)	(63,875)
Depreciation and amortization									24,619	25,489	$ 21,834
Total assets	$ 489,309								$ 470,825	$ 489,309