Operating Segments Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2018	Oct. 31, 2017
Business to Business Products
Revenue by Principal Product
Net Sales	$ 25,326	$ 27,087
Business to Business Products | Cat Litter
Revenue by Principal Product
Net Sales	3,215	3,800
Business to Business Products | Industrial and Sports
Revenue by Principal Product
Net Sales	0	0
Business to Business Products | Agricultural and Horticultural
Revenue by Principal Product
Net Sales	6,052	6,043
Business to Business Products | Bleaching Clay and Fluids Purification
Revenue by Principal Product
Net Sales	11,895	12,617
Business to Business Products | Animal Health and Nutrition
Revenue by Principal Product
Net Sales	4,164	4,627
Retail and Wholesale Products
Revenue by Principal Product
Net Sales	40,817	39,559
Retail and Wholesale Products | Cat Litter
Revenue by Principal Product
Net Sales	32,395	30,822
Retail and Wholesale Products | Industrial and Sports
Revenue by Principal Product
Net Sales	7,777	8,117
Retail and Wholesale Products | Agricultural and Horticultural
Revenue by Principal Product
Net Sales	0	0
Retail and Wholesale Products | Bleaching Clay and Fluids Purification
Revenue by Principal Product
Net Sales	645	620
Retail and Wholesale Products | Animal Health and Nutrition
Revenue by Principal Product
Net Sales	$ 0	$ 0