Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Feb. 28, 2013	Feb. 29, 2012
OPERATING ACTIVITIES
Net loss	$ (19,594)	$ (52,737)
Adjustments to reconcile net loss to cash provided by operating activities
Depreciation, depletion and amortization	42,968	46,495
(Gains)/Loss on asset disposals	(4,822)	(3,736)
Deferred income tax (benefit) expense	1,025	(1,653)
Stock-based compensation expense	7,015	1,710
Other – net	(7,555)	(4,424)
Changes in operating assets and liabilities
Receivables – net	830	7,624
Inventories	(710)	10,048
Prepaid expenses	(2,158)	3,261
Accounts payable and accrued liabilities	(7,228)	(4,466)
Net cash provided by operating activities	9,771	2,122
INVESTING ACTIVITIES
Capital expenditures – expansions	(61,344)	(64,901)
Capital expenditures – other	(17,752)	(31,394)
Proceeds from asset disposals	5,783	4,188
Investments in life insurance contracts	2,366	3,354
Other – net	(67)	(302)
Net cash used by investing activities	(71,014)	(89,055)
FINANCING ACTIVITIES
Debt payments	(2,236)	(173)
Debt issuance costs	0	(1,829)
Stock option exercises	7,116	1,749
Common dividends paid	0	(2,091)
Net cash provided (used) by financing activities	4,880	(2,344)
Decrease in cash and cash equivalents	(56,363)	(89,277)
Cash and cash equivalents at beginning of period	88,027	116,432
Cash and cash equivalents at end of period	$ 31,664	$ 27,155