INVESTMENT SECURITIES - Realized Gain (Loss) on Securities Sold (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 0	$ 0	$ 53,412
Realized gains	0	0	7
Realized losses	0	0	(597)
Change in unrealized gain (loss) on equity securities reflected in the Consolidated Statements of Operations	$ 0	$ 0	$ (23)
Number of investment securities sold during period | security	0	0