FAIR VALUE MEASUREMENTS (Details) (USD $) In Thousands, unless otherwise specified							3 Months Ended		9 Months Ended
	Feb. 28, 2012 Carrying (Reported) Amount, Fair Value Disclosure [Member]	May 31, 2011 Carrying (Reported) Amount, Fair Value Disclosure [Member]	Feb. 28, 2012 Estimate of Fair Value, Fair Value Disclosure [Member]	May 31, 2011 Estimate of Fair Value, Fair Value Disclosure [Member]	Feb. 28, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member]	May 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member]	Feb. 28, 2012 Fair Value, Measurements, Nonrecurring [Member]	Mar. 01, 2011 Fair Value, Measurements, Nonrecurring [Member]	Feb. 28, 2012 Fair Value, Measurements, Nonrecurring [Member]	Mar. 01, 2011 Fair Value, Measurements, Nonrecurring [Member]	Feb. 28, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]		May 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan - Assets					$ 8,551	$ 8,792
Deferred compensation plan - Liabilities					(8,551)	(8,792)
Total					0	0
Long-lived assets held for sale											58,161	[1]	24,686	[1]
Long-lived assets held for use											4,145		747
Total											62,306		25,433
Long-lived assets held for sale included in construction in progress											19,100		23,300
Long-lived assets held for sale							141	888	347	1,877
Long-lived assets held for use							11,393	0	12,023	349
Total impairment of long-lived assets							11,534	888	12,370	2,226
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred Compensation Plan investment in RTI common stock	1,487	1,556	1,205	1,653
Long-term debt and capital leases	307,248	344,274	311,500	348,272
Letters of credit	$ 0	$ 0	$ 222	$ 178

[1] Included in the carrying value of long-lived assets held for sale as of February 28, 2012 and May 31, 2011 are $19.1 million and $23.3 million, respectively, of assets included in Construction in progress in the Condensed Consolidated Balance Sheets as we do not expect to sell these assets within the next 12 months.