Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data	Aug. 31, 2011	May 31, 2011
Condensed Consolidated Balance Sheets
Accounts receivable, allowances (in dollars)	$ 5,615	$ 5,719
Property, plant and equipment, accumulated depreciation	$ 246,183	$ 235,098
Preferred stock, par value (in dollars per share)	$ 1.00	$ 1.00
Preferred stock, authorized shares	250	250
Preferred stock, issued shares	0	0
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, authorized shares	100,000	100,000
Common stock, issued shares	44,934	44,986
Treasury stock, shares	4,473	5,205