LOANS AND ALLOWANCE FOR LOAN LOSSES (Changes in Carrying Amount and Accretable Yield for Purchased Impaired and Nonimpaired Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Loan and Leases Receivable Recorded Investment Schedule [Roll Forward]
Balance at beginning of period	$ 2,178,961
Balance at end of period	2,185,635	$ 2,178,961
GAB acquisition [Member]
Loan and Leases Receivable Recorded Investment Schedule [Roll Forward]
Balance at beginning of period	807,208
Balance at end of period	620,368	807,208
Receivables Acquired with Deteriorated Credit Quality [Member] | GAB acquisition [Member]
Loans and Leases Receivable Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	174	315
Accretion	(72)	(141)
Balance at ending of period	102	174
Loan and Leases Receivable Recorded Investment Schedule [Roll Forward]
Balance at beginning of period	11,449	13,614
Accretion	72	141
Payments received	(2,322)	(2,306)
Balance at end of period	9,199	11,449
Receivables Acquired Without Deteriorated Credit Quality [Member] | GAB acquisition [Member]
Loans and Leases Receivable Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	13,474	17,460
Accretion	(3,549)	(4,196)
Reclassifications from nonaccretable balance		210
Balance at ending of period	9,925	13,474
Loan and Leases Receivable Recorded Investment Schedule [Roll Forward]
Balance at beginning of period	795,759	1,011,801
Accretion	3,549	4,196
Payments received	(188,139)	(220,238)
Balance at end of period	$ 611,169	$ 795,759