MARKETABLE SECURITIES - Securities in Continuous Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Gross Unrealized Losses
Less Than 12 Months	$ 0	$ (638)
12 Months or Longer	(588)	(6,459)
Total	(588)	(7,097)
Estimated Fair Value
Less Than 12 Months	0	29,860
12 Months or Longer	67,157	191,232
Total	67,157	221,092
Gross Unrealized Losses
Less Than 12 Months	(6)	(561)
12 Months or Longer	(45)	(1,061)
Total	(51)	(1,622)
Estimated Fair Value
Less Than 12 Months	3,029	59,442
12 Months or Longer	8,050	38,828
Total	11,079	98,270
Corporate bonds
Gross Unrealized Losses
Less Than 12 Months	0	(453)
12 Months or Longer	0	(336)
Total	0	(789)
Estimated Fair Value
Less Than 12 Months	0	11,236
12 Months or Longer	0	7,718
Total	0	18,954
Mortgage-backed securities
Gross Unrealized Losses
Less Than 12 Months	0	(89)
12 Months or Longer	(555)	(3,587)
Total	(555)	(3,676)
Estimated Fair Value
Less Than 12 Months	0	7,173
12 Months or Longer	64,192	76,717
Total	64,192	83,890
Gross Unrealized Losses
Less Than 12 Months	0	(21)
12 Months or Longer	(43)	(479)
Total	(43)	(500)
Estimated Fair Value
Less Than 12 Months	0	1,478
12 Months or Longer	7,287	12,317
Total	7,287	13,795
Collateralized mortgage obligations
Gross Unrealized Losses
Less Than 12 Months	0	(79)
12 Months or Longer	(33)	(2,293)
Total	(33)	(2,372)
Estimated Fair Value
Less Than 12 Months	0	9,232
12 Months or Longer	2,965	99,390
Total	2,965	108,622
Gross Unrealized Losses
Less Than 12 Months	0	(28)
12 Months or Longer	0	0
Total	0	(28)
Estimated Fair Value
Less Than 12 Months	13	2,171
12 Months or Longer	0	0
Total	13	2,171
Municipal securities
Gross Unrealized Losses
Less Than 12 Months	0	(17)
12 Months or Longer	0	(243)
Total	0	(260)
Estimated Fair Value
Less Than 12 Months	0	2,219
12 Months or Longer	0	7,407
Total	0	9,626
Gross Unrealized Losses
Less Than 12 Months	(6)	(512)
12 Months or Longer	(2)	(582)
Total	(8)	(1,094)
Estimated Fair Value
Less Than 12 Months	3,016	55,793
12 Months or Longer	763	26,511
Total	$ 3,779	$ 82,304