5. FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Money Market Funds - USD ($) $ in Thousands	Aug. 31, 2019	May 31, 2019
Assets
Investment securities	$ 2,029	$ 3,017
Level 1
Assets
Investment securities	2,029	$ 3,017
Level 2
Assets
Investment securities	0
Level 3
Assets
Investment securities	$ 0

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

Name:	us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant