Revenue Recognition - Summary of Net Sales by Geography and Product Line (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019
Disaggregation of Revenue [Line Items]
Net sales	$ 236,933	$ 228,552	$ 782,677	$ 678,679
Capital equipment
Disaggregation of Revenue [Line Items]
Net sales	50,589	51,351	169,061	166,870
Consumables
Disaggregation of Revenue [Line Items]
Net sales	131,486	144,515	438,974	417,067
Product service
Disaggregation of Revenue [Line Items]
Net sales	29,243	31,074	92,374	91,428
Instrument sales
Disaggregation of Revenue [Line Items]
Net sales	25,040	0	79,381	0
All other
Disaggregation of Revenue [Line Items]
Net sales	575	1,612	2,887	3,314
United States
Disaggregation of Revenue [Line Items]
Net sales	176,688	163,367	574,370	497,469
Europe/Africa/Middle East
Disaggregation of Revenue [Line Items]
Net sales	37,518	39,949	128,032	106,278
Asia/Pacific
Disaggregation of Revenue [Line Items]
Net sales	14,766	15,140	54,097	46,476
Canada
Disaggregation of Revenue [Line Items]
Net sales	6,448	8,555	22,026	24,064
Latin America/South America
Disaggregation of Revenue [Line Items]
Net sales	$ 1,513	$ 1,541	$ 4,152	$ 4,392