Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jan. 31, 2020	Jul. 31, 2019
Allowance for doubtful accounts	$ 6,362	$ 5,444
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized shares	10,000	10,000
Preferred stock, shares issued
Common Class A
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	35,000	35,000
Common stock, shares issued	3,272	3,272
Common stock, shares outstanding	1,574	1,574
Treasury stock, common stock shares	1,698	1,698
Common Class B
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	25,961	25,803
Common stock, shares outstanding	25,016	24,895
Treasury stock, common stock shares	945	908