SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES - ASU 2016-13 Impact on Allowance (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses	$ 49,006	$ 24,797	$ 24,797	$ 27,019	$ 20,781
Allowance for off-balance-sheet credit exposures	6,386	1,455	1,455	1,890	1,971
Post-Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		30,100
Allowance for off-balance-sheet credit exposures		6,295
Impact of CECL adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		5,303
Allowance for off-balance-sheet credit exposures	4,840	4,840	0	0
Construction real estate loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses	6,490	3,539	3,539	3,597	3,676
Construction real estate loans | Post-Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		6,492
Construction real estate loans | Impact of CECL adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		2,953
1-4 family residential real estate loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses	2,270	3,833	3,833	3,844	2,445
1-4 family residential real estate loans | Post-Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		2,380
1-4 family residential real estate loans | Impact of CECL adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		(1,453)
Commercial real estate loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses	35,709	9,572	9,572	13,968	10,821
Commercial real estate loans | Post-Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		17,635
Commercial real estate loans | Impact of CECL adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		8,063
Commercial loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses	4,107	6,351	6,351	3,974	2,094
Commercial loans | Post-Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		2,797
Commercial loans | Impact of CECL adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		(3,554)
Municipal loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses	46	570	570	525	860
Municipal loans | Post-Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		48
Municipal loans | Impact of CECL adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		(522)
Loans to individuals
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses	$ 384	932	$ 932	$ 1,111	$ 885
Loans to individuals | Post-Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		748
Loans to individuals | Impact of CECL adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for loan losses		$ (184)