INVESTMENTS (Schedule of Unrealized Gross Losses and Estimated Fair values of Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	$ 10,876	$ 100,011
Unrealized Losses - Less Than 12 Months	(46)	(599)
Fair Value - 12 Months of More	582,441	621,294
Unrealized Losses - 12 Months or More	(13,723)	(23,937)
Fair Value	593,317	721,305
Unrealized losses	(13,769)	(24,536)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	509
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(5)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	426	411
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(19)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	426	920
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3)	(24)
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	2,017	36,218
Unrealized Losses - Less Than 12 Months	0	(281)
Fair Value - 12 Months of More	9,941	28,437
Unrealized Losses - 12 Months or More	(105)	(613)
Fair Value	11,958	64,655
Unrealized losses	(105)	(894)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	509
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(5)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	426	411
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(19)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	426	920
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3)	(24)
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	8,859	46,459
Unrealized Losses - Less Than 12 Months	(46)	(252)
Fair Value - 12 Months of More	347,541	364,430
Unrealized Losses - 12 Months or More	(6,403)	(13,272)
Fair Value	356,400	410,889
Unrealized losses	(6,449)	(13,524)
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	0	5,956
Unrealized Losses - Less Than 12 Months	0	(40)
Fair Value - 12 Months of More	224,959	227,461
Unrealized Losses - 12 Months or More	(7,215)	(10,031)
Fair Value	224,959	233,417
Unrealized losses	$ (7,215)	(10,071)
Subordinated corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months		11,378
Unrealized Losses - Less Than 12 Months		(26)
Fair Value - 12 Months of More		966
Unrealized Losses - 12 Months or More		(21)
Fair Value		12,344
Unrealized losses		$ (47)

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

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-Publisher FASB
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