FAIR VALUE DISCLOSURES - Financial instruments measured at fair value on recurring basis (Details) - Fair value on a recurring basis - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Equity securities	$ 101	$ 237
Investments measured at net asset value	27,520	28,476
Level 1
Assets:
Equity securities	$ 101	$ 237

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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