Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Aug. 31, 2012	May 31, 2012
Condensed Consolidated Balance Sheets
Accounts receivable, allowances (in dollars)	$ 6.9	$ 8.2
Property, plant and equipment, accumulated depreciation (in dollars)	$ 308.4	$ 298.4
Preferred stock, par value (in dollars per share)	$ 1.00	$ 1.00
Preferred stock, authorized shares	250,000	250,000
Preferred stock, issued shares	0	0
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, authorized shares	100,000,000	100,000,000
Common stock, issued shares	44,840,546	44,849,196
Treasury stock, shares	4,887,819	4,576,368