INVESTMENT OPERATIONS - Schedule of Realized Gain(Losses) on Equity Securities Sold (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Net gains (losses) recognized during the period on equity securities	$ 7,696	$ (1,044)	$ 38,413	$ (9,830)
Less: net gains (losses) recognized on equity securities sold during the period	193	(680)	253	(2,381)
Gains (losses) recognized during the period on equity securities still held	$ 7,503	$ (364)	$ 38,160	$ (7,449)

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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