LOANS RECEIVABLE AND THE ALLOWANCE FOR CREDIT LOSSES (Age Analysis of Company's Past Due Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total loans	$ 10,611,417	$ 10,146,724
Non-accrual with no Allowance	16,245	12,391
Nonaccrual loans	24,220	21,706
Loans 90 days or more past due and still accruing	2,044	1,287
Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Total loans	911,540	845,320
Non-accrual with no Allowance	0	0
Nonaccrual loans	63	143
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	911,540	845,320
Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Total loans	1,530,087	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	1,530,087	1,589,975
Small Balance Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,169,828	1,200,251
Non-accrual with no Allowance	808	2,927
Nonaccrual loans	1,302	3,540
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,169,828	1,200,251
Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Total loans	766,571	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	766,571	645,071
Commercial construction
Financing Receivable, Past Due [Line Items]
Total loans	168,061	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	168,061	184,876
Multifamily construction
Financing Receivable, Past Due [Line Items]
Total loans	453,129	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	453,129	325,816
One- to four- family construction
Financing Receivable, Past Due [Line Items]
Total loans	536,349	647,329
Non-accrual with no Allowance	4,788	0
Nonaccrual loans	5,040	0
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	536,349	647,329
Land and land development
Financing Receivable, Past Due [Line Items]
Total loans	346,362	328,475
Non-accrual with no Allowance	498	0
Nonaccrual loans	498	181
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	346,362	328,475
Commercial Business
Financing Receivable, Past Due [Line Items]
Total loans	1,263,747	1,283,407
Non-accrual with no Allowance	3,617	6,998
Nonaccrual loans	4,027	7,356
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,263,747	1,283,407
Small business scored
Financing Receivable, Past Due [Line Items]
Total loans	1,000,714	947,092
Non-accrual with no Allowance	287	303
Nonaccrual loans	1,262	2,530
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,000,714	947,092
Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Total loans	334,626	295,077
Non-accrual with no Allowance	3,170	594
Nonaccrual loans	3,170	594
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	334,626	295,077
One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,438,694	1,173,112
Non-accrual with no Allowance	2,256	1,569
Nonaccrual loans	5,480	5,236
Loans 90 days or more past due and still accruing	1,799	1,023
Financing Receivable, before Allowance for Credit Loss	1,438,694	1,173,112
Consumer—home equity revolving lines of credit
Financing Receivable, Past Due [Line Items]
Total loans	579,836	566,291
Non-accrual with no Allowance	821	0
Nonaccrual loans	3,369	2,124
Loans 90 days or more past due and still accruing	245	254
Financing Receivable, before Allowance for Credit Loss	579,836	566,291
Consumer-other
Financing Receivable, Past Due [Line Items]
Total loans	111,873	114,632
Non-accrual with no Allowance	0	0
Nonaccrual loans	9	2
Loans 90 days or more past due and still accruing	0	10
Financing Receivable, before Allowance for Credit Loss	111,873	114,632
30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,743	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	0	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	497	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	1,475	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	0	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	310	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	1,201	1,824
30 to 59 Days Past Due [Member] | Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	260	259
60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,906	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	0	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	42	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	864	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	48	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	1,387	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	475	203
60 to 89 Days Past Due [Member] | Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	90	178
90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	21,663	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	0	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	5,040	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	499	97
90 Days or More Past Due [Member] | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,935	649
90 Days or More Past Due [Member] | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	937	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	2,174	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	6,341	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	2,737	1,582
90 Days or More Past Due [Member] | Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	10
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	28,312	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	0	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	5,040	900
Financial Asset, Past Due | Land and land development
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	541	1,018
Financial Asset, Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,432	6,894
Financial Asset, Past Due | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,276	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	2,222	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	8,038	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	4,413	3,609
Financial Asset, Past Due | Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	350	447
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,583,105	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	911,540	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	1,530,087	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	1,169,828	1,198,390
Financial Asset, Not Past Due | Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	766,571	645,071
Financial Asset, Not Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	168,061	184,876
Financial Asset, Not Past Due | Multifamily construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	453,129	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	531,309	646,429
Financial Asset, Not Past Due | Land and land development
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	345,821	327,457
Financial Asset, Not Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,259,315	1,276,513
Financial Asset, Not Past Due | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	997,438	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	332,404	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	1,430,656	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	575,423	562,682
Financial Asset, Not Past Due | Consumer-other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 111,523	$ 114,185