Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2013	Aug. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (1,379)	$ (3,468)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	490	544
Changes in assets and liabilities:
Accrued interest receivable	1	2
Accounts receivable	479	188
Inventories	(1,119)	(1,391)
Other current assets	(113)	(1,048)
Accounts payable, trade	46	964
Accrued liabilities	2,004	236
Other, net	(234)	(30)
Net cash provided by (used in) operating activities	175	(4,003)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from principal payments of U.S. Treasury Bills	6,999	14,995
Purchase of U.S. Treasury Bills	(10,000)	(13,997)
Proceeds from note receivable	12
Purchase of property, plant and equipment	(4)	(15)
Other, net	112	21
Net cash (used in) provided by investing activities	(2,881)	1,004
Net decrease in cash	(2,706)	(2,999)
Cash at beginning of period	11,838	12,011
Cash at end of period	$ 9,132	$ 9,012