INVESTMENT OPERATIONS - Schedule of Realized Gain(Losses) on Equity Securities Sold (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Net gains (losses) recognized during the period on equity securities	$ 6,310	$ (6,638)	$ 44,723	$ (16,466)
Less: net gains (losses) recognized on equity securities sold during the period	(648)	(1,476)	(395)	(3,856)
Gains (losses) recognized during the period on equity securities still held	$ 6,958	$ (5,162)	$ 45,118	$ (12,610)

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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