Consolidated Statements Of Shareholders' Equity (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Common stock, par value	$ 1	$ 1
Common Stock
Common stock, par value	$ 1	$ 1	$ 1
Retained Earnings
Common dividends paid, per Share	$ 0.075	$ 0.300	$ 0.300
Accumulated Other Comprehensive Income (Loss)
Postretirement benefit obligation adjustments - tax expense (benefit)	$ 1,367	$ 799	$ (270)