LOANS AND ALLOWANCE FOR PROBABLE LOAN LOSSES - Purchased Credit Impaired (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017
Purchased Credit Impaired [Abstract]
Outstanding principal balance	$ 51,388	[1]	$ 52,426
Carrying amount	46,402	[1],[2]	45,233
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	18,721		2,480
Additions due to acquisition	0		15,389
Changes in expected cash flows not affecting non-accretable differences	(1,445)		0
Reclassifications (to) from nonaccretable discount	1,211		1,720
Accretion	(3,433)		(868)
Balance at end of period	15,054		$ 18,721
Pass
Purchased Credit Impaired [Abstract]
Purchased credit impaired loans, new funds to borrower	$ 14,000

[1] At December 31, 2018, PCI totals include approximately $14.0 million in new funds to a borrower that has since been upgraded to a Pass credit.

[2] At December 31, 2018, PCI totals include approximately $14.0 million in new funds to a borrower that has since been upgraded to a Pass credit.