SECURITIES (Schedule of Unrealized Gross Losses and Estimated Fair values of Investment Securities) (Details) $ in Thousands	Jun. 30, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions \| security	187	209
Fair Value - Less Than 12 Months	$ 480,873	$ 511,991
Unrealized Losses - Less Than 12 Months	(5,700)	(8,686)
Fair Value - 12 Months of More	121,640	103,708
Unrealized Losses - 12 Months or More	(4,523)	(3,850)
Fair Value	602,513	615,699
Unrealized losses	(10,223)	(12,536)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	20,686	42,805
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(369)	(631)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	20,686	42,805
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(369)	(631)
AFS and HTM securities in Continues Unrealized Loss Position	623,200	$ 658,500
Unrealized Loss as a Percent of Fair Value		2.00%
AFS and HTM Securities Unrealized Loss Accumulated in Investments	10,600	$ 13,200
Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
AFS and HTM Securities Unrealized Loss Accumulated in Investments	4,500	3,900
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	364,378	348,579
Unrealized Losses - Less Than 12 Months	(4,139)	(5,780)
Fair Value - 12 Months of More	29,988	29,496
Unrealized Losses - 12 Months or More	(1,100)	(1,335)
Fair Value	394,366	378,075
Unrealized losses	(5,239)	(7,115)
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	116,495	163,412
Unrealized Losses - Less Than 12 Months	(1,561)	(2,906)
Fair Value - 12 Months of More	91,652	74,212
Unrealized Losses - 12 Months or More	(3,423)	(2,515)
Fair Value	208,147	237,624
Unrealized losses	(4,984)	(5,421)
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	20,686	42,805
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(369)	(631)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	20,686	42,805
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (369)	$ (631)

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