LOANS RECEIVABLE AND THE ALLOWANCE FOR CREDIT LOSSES (Age Analysis of Company's Past Due Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Total loans	$ 9,456,829	$ 9,084,763
Non-accrual with no Allowance	9,928	11,765
Nonaccrual loans	16,660	22,281
Loans 90 days or more past due and still accruing	2,055	555
Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Total loans	845,184	831,623
Non-accrual with no Allowance	0	924
Nonaccrual loans	258	1,456
Loans 90 days or more past due and still accruing	899	0
Financing Receivable, before Allowance for Credit Loss	845,184	831,623
Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Total loans	1,628,105	1,674,027
Non-accrual with no Allowance	3,127	3,706
Nonaccrual loans	3,812	6,282
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,628,105	1,674,027
Small balance CRE
Financing Receivable, Past Due [Line Items]
Total loans	1,191,903	1,281,863
Non-accrual with no Allowance	5,750	5,886
Nonaccrual loans	5,971	6,421
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	1,191,903	1,281,863
Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Total loans	575,183	530,885
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	575,183	530,885
Commercial construction
Financing Receivable, Past Due [Line Items]
Total loans	193,984	167,998
Non-accrual with no Allowance	0	0
Nonaccrual loans	0	98
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	193,984	167,998
Multifamily construction
Financing Receivable, Past Due [Line Items]
Total loans	256,952	259,116
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	256,952	259,116
One- to four- family construction
Financing Receivable, Past Due [Line Items]
Total loans	625,488	568,753
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	625,488	568,753
Land and land development - residential [Member]
Financing Receivable, Past Due [Line Items]
Total loans	320,041	313,454
Non-accrual with no Allowance	0	0
Nonaccrual loans	200	381
Loans 90 days or more past due and still accruing	0	0
Commercial Business
Financing Receivable, Past Due [Line Items]
Total loans	1,206,938	1,170,780
Non-accrual with no Allowance	29	228
Nonaccrual loans	506	1,144
Loans 90 days or more past due and still accruing	20	2
Financing Receivable, before Allowance for Credit Loss	1,206,938	1,170,780
Small business scored
Financing Receivable, Past Due [Line Items]
Total loans	865,828	792,310
Non-accrual with no Allowance	0	0
Nonaccrual loans	1,015	1,012
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	865,828	792,310
Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Total loans	283,415	280,578
Non-accrual with no Allowance	1,022	1,021
Nonaccrual loans	1,022	1,022
Loans 90 days or more past due and still accruing	0	0
Financing Receivable, before Allowance for Credit Loss	283,415	280,578
One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Total loans	868,175	657,474
Non-accrual with no Allowance	0	0
Nonaccrual loans	2,002	2,711
Loans 90 days or more past due and still accruing	1,053	436
Financing Receivable, before Allowance for Credit Loss	868,175	657,474
Consumer secured by one- to four-family [Member]
Financing Receivable, Past Due [Line Items]
Total loans	506,524	458,533
Non-accrual with no Allowance	0	0
Nonaccrual loans	1,859	1,736
Loans 90 days or more past due and still accruing	73	114
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total loans	89,109	97,369
Non-accrual with no Allowance	0	0
Nonaccrual loans	15	18
Loans 90 days or more past due and still accruing	10	3
30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,626	10,527
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	51	233
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	81
30 to 59 Days Past Due [Member] | Small balance CRE
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	869	89
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	162
30 to 59 Days Past Due [Member] | Land and land development - residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	51
30 to 59 Days Past Due [Member] | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	248	5,157
30 to 59 Days Past Due [Member] | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	978	924
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	139
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	211	2,318
30 to 59 Days Past Due [Member] | Consumer secured by one- to four-family [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	912	985
30 to 59 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	357	388
60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,961	2,142
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	180	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	3,644	0
60 to 89 Days Past Due [Member] | Small balance CRE
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,770	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 - residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	77	1,007
60 to 89 Days Past Due [Member] | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	336	465
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	42	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	606	327
60 to 89 Days Past Due [Member] | Consumer secured by one- to four-family [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	210	268
60 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	96	75
90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,536	6,019
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	899	448
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 CRE
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2	1,298
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	98
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	0	0
90 Days or More Past Due [Member] | Land and land development - residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	14
90 Days or More Past Due [Member] | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	128	588
90 Days or More Past Due [Member] | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	494	508
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	1,022	1,021
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	2,217	1,225
90 Days or More Past Due [Member] | Consumer secured by one- to four-family [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	752	803
90 Days or More Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	22	16
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	18,123	18,688
Financial Asset, Past Due | Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,130	681
Financial Asset, Past Due | Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,644	81
Financial Asset, Past Due | Small balance CRE
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,641	1,387
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	98
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	0	162
Financial Asset, Past Due | Land and land development - residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	65
Financial Asset, Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	453	6,752
Financial Asset, Past Due | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,808	1,897
Financial Asset, Past Due | Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,064	1,160
Financial Asset, Past Due | One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,034	3,870
Financial Asset, Past Due | Consumer secured by one- to four-family [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,874	2,056
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	475	479
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	9,438,706	9,066,075
Financial Asset, Not Past Due | Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	844,054	830,942
Financial Asset, Not Past Due | Commercial real estate - investment properties
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,624,461	1,673,946
Financial Asset, Not Past Due | Small balance CRE
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,187,262	1,280,476
Financial Asset, Not Past Due | Multifamily Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	575,183	530,885
Financial Asset, Not Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	193,984	167,900
Financial Asset, Not Past Due | Multifamily construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	256,952	259,116
Financial Asset, Not Past Due | One- to four- family construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	625,488	568,591
Financial Asset, Not Past Due | Land and land development - residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	320,041	313,389
Financial Asset, Not Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,206,485	1,164,028
Financial Asset, Not Past Due | Small business scored
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	864,020	790,413
Financial Asset, Not Past Due | Agricultural business, including secured by farmland
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	282,351	279,418
Financial Asset, Not Past Due | One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	865,141	653,604
Financial Asset, Not Past Due | Consumer secured by one- to four-family [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	504,650	456,477
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 88,634	$ 96,890