INVESTMENT OPERATIONS - Schedule of Realized Gain(Losses) on Equity Securities Sold (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Net gains (losses) recognized during the period on equity securities	$ (8,786)	$ (9)
Less: net gains (losses) recognized on equity securities sold during the period	(1,702)
Gains (losses) recognized during the period on equity securities still held	$ (7,084)