INVESTMENT OPERATIONS - Schedule of Realized Gain (Losses) on Equity Securities Sold (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Net gains (losses) recognized during the period on equity securities	$ 30,635	$ (8,738)
Less: net gains (losses) recognized on equity securities sold during the period	60	(1,702)
Gains (losses) recognized during the period on equity securities still held	$ 30,575	$ (7,036)

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=84241550&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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