MARKETABLE SECURITIES - Securities in Continuous Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Gross Unrealized Losses
Less Than 12 Months	$ (1,695)	$ (2,483)
12 Months or Longer	(660)	(790)
Total	(2,355)	(3,273)
Estimated Fair Value
Less Than 12 Months	124,156	129,603
12 Months or Longer	23,515	24,319
Total	147,671	153,922
Gross Unrealized Losses
Less Than 12 Months	(2,605)	(4,179)
12 Months or Longer	(809)	(521)
Total	(3,414)	(4,700)
Estimated Fair Value
Less Than 12 Months	102,740	118,926
12 Months or Longer	8,202	2,350
Total	110,942	121,276
Corporate bonds
Gross Unrealized Losses
Less Than 12 Months	(123)	(377)
12 Months or Longer	0	0
Total	(123)	(377)
Estimated Fair Value
Less Than 12 Months	12,508	22,529
12 Months or Longer	0	0
Total	12,508	22,529
Municipal securities
Gross Unrealized Losses
Less Than 12 Months	(539)	(622)
12 Months or Longer	0	0
Total	(539)	(622)
Estimated Fair Value
Less Than 12 Months	7,278	7,219
12 Months or Longer	0	0
Total	7,278	7,219
Mortgage-backed securities
Gross Unrealized Losses
Less Than 12 Months	(761)	(1,047)
12 Months or Longer	(475)	(561)
Total	(1,236)	(1,608)
Estimated Fair Value
Less Than 12 Months	62,344	44,420
12 Months or Longer	14,870	15,270
Total	77,214	59,690
Collateralized mortgage obligations
Gross Unrealized Losses
Less Than 12 Months	(272)	(437)
12 Months or Longer	(185)	(229)
Total	(457)	(666)
Estimated Fair Value
Less Than 12 Months	42,026	55,435
12 Months or Longer	8,645	9,049
Total	50,671	64,484
Municipal securities
Gross Unrealized Losses
Less Than 12 Months	(2,414)	(3,889)
12 Months or Longer	(207)	0
Total	(2,621)	(3,889)
Estimated Fair Value
Less Than 12 Months	84,716	98,943
12 Months or Longer	5,965	0
Total	90,681	98,943
Mortgage-backed securities
Gross Unrealized Losses
Less Than 12 Months	(191)	(290)
12 Months or Longer	0	0
Total	(191)	(290)
Estimated Fair Value
Less Than 12 Months	18,024	19,983
12 Months or Longer	0	0
Total	18,024	19,983
Collateralized mortgage obligations
Gross Unrealized Losses
Less Than 12 Months	0	0
12 Months or Longer	(602)	(521)
Total	(602)	(521)
Estimated Fair Value
Less Than 12 Months	0	0
12 Months or Longer	2,237	2,350
Total	$ 2,237	$ 2,350