Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Aug. 31, 2019	Aug. 31, 2018
Statement Of Financial Position [Abstract]
Receivables, allowance	$ 2,635	$ 3,585
Preferred stock, par value	$ 1	$ 1
Preferred stock, authorized	2,000,000	2,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 1	$ 1
Common stock, authorized	25,000,000	25,000,000
Common stock, issued	18,870,000	18,841,000
Treasury stock, shares	8,083,000	8,083,000