Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Aug. 31, 2019	May 31, 2019
Accounts receivable, allowance	$ 1,700	$ 1,700
Accumulated Amortization	$ 40,127	$ 40,835
Preferred stock, par value	$ 1.00	$ 1.00
Preferred stock, shares authorized	100,000	100,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.16	$ 0.16
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	52,422,942	52,216,589
Common stock, shares outstanding	52,422,942	52,216,589