MARKETABLE SECURITIES - Schedule of Amortized Cost and Fair Value of Securities Available for Sale and Held to Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available for sale:
Available-for-sale debt securities, amortized cost basis	$ 351,130	$ 210,212
Gross Unrealized Gain	17,903	2,864
Gross Unrealized Loss	146	360
Estimated Fair Value	368,887	212,716
Held to maturity:
Amortized Cost	0	155,458
Gross Unrealized Gains		5,018
Gross Unrealized Losses		16
Estimated Fair Value		160,460
Corporate bonds
Available for sale:
Available-for-sale debt securities, amortized cost basis	18,619	19,667
Gross Unrealized Gain	1,260	592
Gross Unrealized Loss		0
Estimated Fair Value	19,879	20,259
Mortgage-backed securities
Available for sale:
Available-for-sale debt securities, amortized cost basis	95,415	83,967
Gross Unrealized Gain	3,099	550
Gross Unrealized Loss	143	335
Estimated Fair Value	98,371	84,182
Held to maturity:
Amortized Cost		14,365
Gross Unrealized Gains		198
Gross Unrealized Losses		13
Estimated Fair Value		14,550
Collateralized mortgage obligations
Available for sale:
Available-for-sale debt securities, amortized cost basis	72,714	89,798
Gross Unrealized Gain	2,618	1,146
Gross Unrealized Loss	3	17
Estimated Fair Value	75,329	90,927
Held to maturity:
Amortized Cost		2,677
Gross Unrealized Gains		110
Gross Unrealized Losses		0
Estimated Fair Value		2,787
Municipal securities
Available for sale:
Available-for-sale debt securities, amortized cost basis	164,382	16,780
Gross Unrealized Gain	10,926	576
Gross Unrealized Loss		8
Estimated Fair Value	$ 175,308	17,348
Held to maturity:
Amortized Cost		138,416
Gross Unrealized Gains		4,710
Gross Unrealized Losses		3
Estimated Fair Value		$ 143,123

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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