LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Age Analysis of Company's Past Due Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Loans receivable	$ 10,810,455	$ 10,146,724
Financing Receivable, Nonaccrual, No Allowance	11,714	12,391
Financing Receivable, Nonaccrual	26,857	21,706
Loans 90 Days or More Past Due and Accruing	2,745	1,287
Commerical real estate - owner-occupied [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	915,897	845,320
Loans receivable	915,897	845,320
Financing Receivable, Nonaccrual, No Allowance	1,391	0
Financing Receivable, Nonaccrual	1,450	143
Loans 90 Days or More Past Due and Accruing	0	0
Commercial real estate - investment properties [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,541,344	1,589,975
Loans receivable	1,541,344	1,589,975
Financing Receivable, Nonaccrual, No Allowance	0	0
Financing Receivable, Nonaccrual	0	0
Loans 90 Days or More Past Due and Accruing	0	0
Small Balance CRE [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,178,500	1,200,251
Loans receivable	1,178,500	1,200,251
Financing Receivable, Nonaccrual, No Allowance	755	2,927
Financing Receivable, Nonaccrual	1,227	3,540
Loans 90 Days or More Past Due and Accruing	0	0
Multifamily real estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	811,232	645,071
Loans receivable	811,232	645,071
Financing Receivable, Nonaccrual, No Allowance	0	0
Financing Receivable, Nonaccrual	0	0
Loans 90 Days or More Past Due and Accruing	0	0
Commercial Construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	170,011	184,876
Loans receivable	170,011	184,876
Financing Receivable, Nonaccrual, No Allowance	0	0
Financing Receivable, Nonaccrual	0	0
Loans 90 Days or More Past Due and Accruing	0	0
Multifamily construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	503,993	325,816
Loans receivable	503,993	325,816
Financing Receivable, Nonaccrual, No Allowance	0	0
Financing Receivable, Nonaccrual	0	0
Loans 90 Days or More Past Due and Accruing	0	0
One-to four-family construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	526,432	647,329
Loans receivable	526,432	647,329
Financing Receivable, Nonaccrual, No Allowance	2,852	0
Financing Receivable, Nonaccrual	3,105	0
Loans 90 Days or More Past Due and Accruing	1,096	0
Land and Land Improvements [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	336,639	328,475
Loans receivable	336,639	328,475
Financing Receivable, Nonaccrual, No Allowance	0	0
Financing Receivable, Nonaccrual	0	181
Loans 90 Days or More Past Due and Accruing	42	0
Commercial business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,255,734	1,283,407
Loans receivable	1,255,734	1,283,407
Financing Receivable, Nonaccrual, No Allowance	789	6,998
Financing Receivable, Nonaccrual	7,346	7,356
Loans 90 Days or More Past Due and Accruing	0	0
Small Credit-Scored Business Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,022,154	947,092
Loans receivable	1,022,154	947,092
Financing Receivable, Nonaccrual, No Allowance	0	303
Financing Receivable, Nonaccrual	1,656	2,530
Loans 90 Days or More Past Due and Accruing	1	0
Agricultural business, including secured by farmland [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	331,089	295,077
Loans receivable	331,089	295,077
Financing Receivable, Nonaccrual, No Allowance	3,167	594
Financing Receivable, Nonaccrual	3,167	594
Loans 90 Days or More Past Due and Accruing	0	0
One- to four-family residential [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,518,046	1,173,112
Loans receivable	1,518,046	1,173,112
Financing Receivable, Nonaccrual, No Allowance	1,939	1,569
Financing Receivable, Nonaccrual	5,702	5,236
Loans 90 Days or More Past Due and Accruing	1,205	1,023
Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	588,703	566,291
Loans receivable	588,703	566,291
Financing Receivable, Nonaccrual, No Allowance	821	0
Financing Receivable, Nonaccrual	3,110	2,124
Loans 90 Days or More Past Due and Accruing	391	254
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	110,681	114,632
Loans receivable	110,681	114,632
Financing Receivable, Nonaccrual, No Allowance	0	0
Financing Receivable, Nonaccrual	94	2
Loans 90 Days or More Past Due and Accruing	10	10
30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	15,936	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 [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] | Small Balance CRE [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	559	1,859
30 to 59 Days Past Due [Member] | Multifamily real estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] | Commercial Construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
30 to 59 Days Past Due [Member] | Multifamily construction [Member]
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 [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	286	900
30 to 59 Days Past Due [Member] | Land and Land Improvements [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,822	921
30 to 59 Days Past Due [Member] | Commercial business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,166	2,100
30 to 59 Days Past Due [Member] | Small Credit-Scored Business Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,050	1,479
30 to 59 Days Past Due [Member] | Agricultural business, including secured by farmland [Member]
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	6,864	5,287
30 to 59 Days Past Due [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,772	1,824
30 to 59 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	417	259
60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,280	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 [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] | Small Balance CRE [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 [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] | Commercial Construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
60 to 89 Days Past Due [Member] | Multifamily construction [Member]
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 [Member]
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 Improvements [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	553	0
60 to 89 Days Past Due [Member] | Commercial business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,735	4,145
60 to 89 Days Past Due [Member] | Small Credit-Scored Business Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	633	661
60 to 89 Days Past Due [Member] | Agricultural business, including secured by farmland [Member]
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	2,379	2,242
60 to 89 Days Past Due [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	839	203
60 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	141	178
90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	16,948	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 [Member]
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 [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	413	2
90 Days or More Past Due [Member] | Multifamily real estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
90 Days or More Past Due [Member] | Commercial Construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
90 Days or More Past Due [Member] | Multifamily construction [Member]
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 [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,201	0
90 Days or More Past Due [Member] | Land and Land Improvements [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	42	97
90 Days or More Past Due [Member] | Commercial business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,181	649
90 Days or More Past Due [Member] | Small Credit-Scored Business Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	959	1,019
90 Days or More Past Due [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,171	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	5,258	5,175
90 Days or More Past Due [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,627	1,582
90 Days or More Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	96	10
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	43,164	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 [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due | Small Balance CRE [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	972	1,861
Financial Asset, Past Due | Multifamily real estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due | Commercial Construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due | Multifamily construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due | One-to four-family construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,487	900
Financial Asset, Past Due | Land and Land Improvements [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,417	1,018
Financial Asset, Past Due | Commercial business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,082	6,894
Financial Asset, Past Due | Small Credit-Scored Business Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,642	3,159
Financial Asset, Past Due | Agricultural business, including secured by farmland [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,171	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	14,501	12,704
Financial Asset, Past Due | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,238	3,609
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	654	447
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,767,291	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	915,897	845,320
Financial Asset, Not Past Due | Commercial real estate - investment properties [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,541,344	1,589,975
Financial Asset, Not Past Due | Small Balance CRE [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,177,528	1,198,390
Financial Asset, Not Past Due | Multifamily real estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	811,232	645,071
Financial Asset, Not Past Due | Commercial Construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	170,011	184,876
Financial Asset, Not Past Due | Multifamily construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	503,993	325,816
Financial Asset, Not Past Due | One-to four-family construction [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	521,945	646,429
Financial Asset, Not Past Due | Land and Land Improvements [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	334,222	327,457
Financial Asset, Not Past Due | Commercial business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,247,652	1,276,513
Financial Asset, Not Past Due | Small Credit-Scored Business Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,018,512	943,933
Financial Asset, Not Past Due | Agricultural business, including secured by farmland [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	328,918	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	1,503,545	1,160,408
Financial Asset, Not Past Due | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	582,465	562,682
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 110,027	$ 114,185