LOANS AND ALLOWANCE FOR PROBABLE LOAN LOSSES - Nonaccrual Loans by Class (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	[1],[2]	$ 35,770	$ 2,937
Construction Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans		12	86
1-4 Family Residential Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans		2,202	1,098
Commercial Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans		32,599	595
Commercial Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans		639	903
Loans to Individuals
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans		$ 318	$ 255

[1] Excludes PCI loans measured at fair value at acquisition if the timing and amount of cash flows expected to be collected from those sales can be reasonably estimated. The increase in nonaccrual loans was primarily due to the addition of four commercial real estate loans to nonaccrual status during the year, one of which was added during the fourth quarter.

[2] Includes $10.9 million and $1.3 million of restructured loans as of December 31, 2018 and 2017, respectively.