Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Nov. 30, 2012	Nov. 30, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (5,193)	$ (10,267)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,032	1,203
Gain on sale of idle property, plant and equipment	(1,411)	(2,500)
Change in assets and liabilities:
Restricted cash	(600)
Accrued interest receivable	3	5
Accounts receivable	2,843	3,533
Inventories	(2,352)	(1,314)
Other current assets	(1,067)	360
Accounts payable, trade	(382)	(728)
Accrued liabilities	1,374	1,963
Other, net	(37)	31
Net cash used in operating activities	(5,790)	(7,714)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from principal payments of U.S. Treasury Bills	34,991	34,985
Purchase of U.S. Treasury Bills	(31,994)	(30,991)
Proceeds from sale of idle property, plant and equipment	348	4,071
Purchase of property, plant and equipment	(26)	(466)
Other, net	130	(45)
Net cash provided by investing activities	3,449	7,554
CASH FLOWS FROM FINANCING ACTIVITIES:
Cash dividends paid		(1,511)
Net cash used in financing activities		(1,511)
Net decrease in cash	(2,341)	(1,671)
Cash at beginning of period	12,011	9,727
Cash at end of period	9,670	8,056
NON-CASH TRANSACTIONS:
Note receivable from sale of idle property, plant and equipment	$ 1,700