LOANS AND ALLOWANCE FOR PROBABLE LOAN LOSSES - Nonaccrual Loans by Class (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	[1],[2]	$ 4,963	$ 35,770
Construction real estate loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans		405	12
1-4 family residential real estate loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans		2,611	2,202
Commercial real estate loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans		704	32,599
Commercial loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans		944	639
Loans to individuals
Financing Receivable, Past Due [Line Items]
Nonaccrual loans		$ 299	$ 318

[1] Includes $469,000 and $10.9 million of restructured loans as of December 31, 2019 and 2018, respectively.

[2] 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.