Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Aug. 31, 2016	May 31, 2016
CONDENSED CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowances (in dollars)	$ 4.8	$ 3.9
Property, plant and equipment, accumulated depreciation (in dollars)	447.9	437.7
Intangible assets, accumulated amortization (in dollars)	$ 26.3	$ 26.5
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	45,161,322	44,867,703
Treasury stock, shares	10,987,009	10,353,153