LOANS RECEIVABLE AND THE ALLOWANCE FOR CREDIT LOSSES (Age Analysis of Company's Past Due Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total loans	$ 10,472,407	$ 10,146,724
Non-accrual with no Allowance	18,635	12,391
Nonaccrual loans	28,071	21,706
Loans 90 days or more past due and still accruing	109	1,287
Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Total loans	894,876	845,320
Non-accrual with no Allowance	0	0
Nonaccrual loans	66	143
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	894,876	845,320
Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Total loans	1,558,176	1,589,975
Non-accrual with no Allowance	0	0
Nonaccrual loans	0	0
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,558,176	1,589,975
Small Balance Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,172,825	1,200,251
Non-accrual with no Allowance	1,865	2,927
Nonaccrual loans	2,412	3,540
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,172,825	1,200,251
Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Total loans	699,830	645,071
Non-accrual with no Allowance	0	0
Nonaccrual loans	0	0
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	699,830	645,071
Commercial construction
Financing Receivable, Past Due [Line Items]
Total loans	183,765	184,876
Non-accrual with no Allowance	0	0
Nonaccrual loans	0	0
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	183,765	184,876
Multifamily construction
Financing Receivable, Past Due [Line Items]
Total loans	433,868	325,816
Non-accrual with no Allowance	0	0
Nonaccrual loans	0	0
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	433,868	325,816
One- to four- family construction
Financing Receivable, Past Due [Line Items]
Total loans	547,200	647,329
Non-accrual with no Allowance	1,711	0
Nonaccrual loans	1,711	0
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	547,200	647,329
Land and land development
Financing Receivable, Past Due [Line Items]
Total loans	345,053	328,475
Non-accrual with no Allowance	499	0
Nonaccrual loans	569	181
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	345,053	328,475
Commercial Business
Financing Receivable, Past Due [Line Items]
Total loans	1,313,226	1,283,407
Non-accrual with no Allowance	5,979	6,998
Nonaccrual loans	6,397	7,356
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,313,226	1,283,407
Small business scored
Financing Receivable, Past Due [Line Items]
Total loans	982,283	947,092
Non-accrual with no Allowance	284	303
Nonaccrual loans	2,042	2,530
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	982,283	947,092
Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Total loans	310,120	295,077
Non-accrual with no Allowance	3,997	594
Nonaccrual loans	3,997	594
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	310,120	295,077
One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,340,126	1,173,112
Non-accrual with no Allowance	3,479	1,569
Nonaccrual loans	7,605	5,236
Loans 90 days or more past due and still accruing	60	1,023
Financing Receivable, before Allowance for Credit Loss	1,340,126	1,173,112
Consumer—home equity revolving lines of credit
Financing Receivable, Past Due [Line Items]
Total loans	577,725	566,291
Non-accrual with no Allowance	821	0
Nonaccrual loans	3,258	2,124
Loans 90 days or more past due and still accruing	49	254
Financing Receivable, before Allowance for Credit Loss	577,725	566,291
Consumer-other
Financing Receivable, Past Due [Line Items]
Total loans	113,334	114,632
Non-accrual with no Allowance	0	0
Nonaccrual loans	14	2
Loans 90 days or more past due and still accruing	0	10
Financing Receivable, before Allowance for Credit Loss	113,334	114,632
30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,826	15,814
30 to 59 Days Past Due [Member] \| Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] \| Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] \| Small Balance Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,560	1,859
30 to 59 Days Past Due [Member] \| Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] \| Commercial construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] \| Multifamily construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] \| One- to four- family construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	900
30 to 59 Days Past Due [Member] \| Land and land development
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	921
30 to 59 Days Past Due [Member] \| Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	17	2,100
30 to 59 Days Past Due [Member] \| Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	538	1,479
30 to 59 Days Past Due [Member] \| Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,724	1,185
30 to 59 Days Past Due [Member] \| One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	615	5,287
30 to 59 Days Past Due [Member] \| Consumer—home equity revolving lines of credit
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,131	1,824
30 to 59 Days Past Due [Member] \| Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	241	259
60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,347	7,429
60 to 89 Days Past Due [Member] \| Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] \| Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] \| Small Balance Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] \| Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] \| Commercial construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] \| Multifamily construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] \| One- to four- family construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,255	0
60 to 89 Days Past Due [Member] \| Land and land development
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	498	0
60 to 89 Days Past Due [Member] \| Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	4,145
60 to 89 Days Past Due [Member] \| Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	82	661
60 to 89 Days Past Due [Member] \| Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] \| One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	998	2,242
60 to 89 Days Past Due [Member] \| Consumer—home equity revolving lines of credit
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	458	203
60 to 89 Days Past Due [Member] \| Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	56	178
90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	19,962	9,128
90 Days or More Past Due [Member] \| Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
90 Days or More Past Due [Member] \| Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
90 Days or More Past Due [Member] \| Small Balance Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2	2
90 Days or More Past Due [Member] \| Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
90 Days or More Past Due [Member] \| Commercial construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
90 Days or More Past Due [Member] \| Multifamily construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
90 Days or More Past Due [Member] \| One- to four- family construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	709	0
90 Days or More Past Due [Member] \| Land and land development
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	97
90 Days or More Past Due [Member] \| Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,290	649
90 Days or More Past Due [Member] \| Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,150	1,019
90 Days or More Past Due [Member] \| Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,952	594
90 Days or More Past Due [Member] \| One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,501	5,175
90 Days or More Past Due [Member] \| Consumer—home equity revolving lines of credit
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,354	1,582
90 Days or More Past Due [Member] \| Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4	10
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	29,135	32,371
Financial Asset, Past Due \| Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due \| Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due \| Small Balance Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,562	1,861
Financial Asset, Past Due \| Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due \| Commercial construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due \| Multifamily construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due \| One- to four- family construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,964	900
Financial Asset, Past Due \| Land and land development
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	498	1,018
Financial Asset, Past Due \| Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,307	6,894
Financial Asset, Past Due \| Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,770	3,159
Financial Asset, Past Due \| Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,676	1,779
Financial Asset, Past Due \| One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,114	12,704
Financial Asset, Past Due \| Consumer—home equity revolving lines of credit
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,943	3,609
Financial Asset, Past Due \| Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	301	447
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,443,272	10,114,353
Financial Asset, Not Past Due \| Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	894,876	845,320
Financial Asset, Not Past Due \| Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,558,176	1,589,975
Financial Asset, Not Past Due \| Small Balance Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,171,263	1,198,390
Financial Asset, Not Past Due \| Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	699,830	645,071
Financial Asset, Not Past Due \| Commercial construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	183,765	184,876
Financial Asset, Not Past Due \| Multifamily construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	433,868	325,816
Financial Asset, Not Past Due \| One- to four- family construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	545,236	646,429
Financial Asset, Not Past Due \| Land and land development
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	344,555	327,457
Financial Asset, Not Past Due \| Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,306,919	1,276,513
Financial Asset, Not Past Due \| Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	980,513	943,933
Financial Asset, Not Past Due \| Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	305,444	293,298
Financial Asset, Not Past Due \| One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,332,012	1,160,408
Financial Asset, Not Past Due \| Consumer—home equity revolving lines of credit
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	573,782	562,682
Financial Asset, Not Past Due \| Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 113,033	$ 114,185

LOANS RECEIVABLE AND THE ALLOWANCE FOR CREDIT LOSSES (Age Analysis of Company's Past Due Loans) (Details) - USD ($)
$ in Thousands

Jun. 30, 2023

Dec. 31, 2022

Financing Receivable, Past Due [Line Items]

Total loans

$ 10,472,407

$ 10,146,724

Non-accrual with no Allowance

18,635

12,391

Nonaccrual loans

28,071