LOANS HELD FOR INVESTMENT, NET - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	$ 10,116,941	$ 9,244,661
Loans held for investment, net of fees and costs	10,116,941	9,244,661
Pass
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	9,728,056	8,531,760
2022	2,198,248
2021	1,764,434	1,828,115
2020	1,264,780	1,473,478
2019	1,014,976	1,174,655
2018	546,117	606,030
2017 and Prior	2,262,606	752,529
2016 and Prior		2,114,513
Revolving	647,221	552,538
Revolving-Term	29,674	29,902
Loans held for investment, net of fees and costs	9,728,056	8,531,760
Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	180,575	173,964
2022	7,230
2021		6,003
2020	942	15,891
2019	59,040	54,365
2018	27,747	21,926
2017 and Prior	75,333	23,775
2016 and Prior		45,900
Revolving	9,049	4,071
Revolving-Term	1,234	2,033
Loans held for investment, net of fees and costs	180,575	173,964
Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	179,549	496,912
2022	4,916
2021	1,209	4,833
2020	24,542	11,011
2019	19,892	50,235
2018	32,419	97,994
2017 and Prior	72,766	91,019
2016 and Prior		196,506
Revolving	12,635	30,823
Revolving-Term	11,170	14,491
Loans held for investment, net of fees and costs	179,549	496,912
Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	19,834	25,127
2021	412	550
2020		1,621
2019	8,332	10,074
2018	752	775
2017 and Prior	10,338	11,107
Revolving		1,000
Loans held for investment, net of fees and costs	19,834	25,127
Total real estate loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	9,195,863	8,294,204
Loans held for investment, net of fees and costs	9,195,863	8,294,204
Excludes Other Loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	10,108,014	9,227,763
2022	2,210,394
2021	1,766,055	1,839,501
2020	1,290,264	1,502,001
2019	1,102,240	1,289,329
2018	607,035	726,725
2017 and Prior	2,421,043	878,430
2016 and Prior		2,356,919
Revolving	668,905	588,432
Revolving-Term	42,078	46,426
Loans held for investment, net of fees and costs	10,108,014	9,227,763
One-to-four family residential and cooperative/condominium apartment
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	722,081	669,282
2022	155,591
2021	110,542	129,679
2020	76,795	89,096
2019	67,182	82,568
2018	68,124	76,726
2017 and Prior	185,115	80,365
2016 and Prior		145,946
Revolving	45,152	50,724
Revolving-Term	13,580	14,178
Loans held for investment, net of fees and costs	722,081	669,282
One-to-four family residential and cooperative/condominium apartment | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	703,484	640,776
2022	155,591
2021	110,542	129,679
2020	75,764	86,028
2019	65,953	80,195
2018	66,976	75,354
2017 and Prior	172,012	77,829
2016 and Prior		129,276
Revolving	44,573	49,878
Revolving-Term	12,073	12,537
Loans held for investment, net of fees and costs	703,484	640,776
One-to-four family residential and cooperative/condominium apartment | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	4,894	6,296
2020		1,124
2019		335
2018	739	752
2017 and Prior	2,845	334
2016 and Prior		2,158
Revolving	579	846
Revolving-Term	731	747
Loans held for investment, net of fees and costs	4,894	6,296
One-to-four family residential and cooperative/condominium apartment | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	13,703	22,187
2020	1,031	1,944
2019	1,229	2,038
2018	409	597
2017 and Prior	10,258	2,202
2016 and Prior		14,512
Revolving-Term	776	894
Loans held for investment, net of fees and costs	13,703	22,187
One-to-four family residential and cooperative/condominium apartment | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans		23
2018		23
Loans held for investment, net of fees and costs		23
Multifamily residential and residential mixed-use
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	3,968,244	3,356,346
2022	1,208,492
2021	585,735	590,462
2020	338,510	353,747
2019	425,928	505,089
2018	158,935	183,616
2017 and Prior	1,238,304	398,804
2016 and Prior		1,309,248
Revolving	12,340	14,555
Revolving-Term		825
Loans held for investment, net of fees and costs	3,968,244	3,356,346
Multifamily residential and residential mixed-use | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	3,790,781	3,029,631
2022	1,208,492
2021	585,735	590,462
2020	326,154	341,206
2019	393,385	455,277
2018	125,893	151,226
2017 and Prior	1,138,782	332,749
2016 and Prior		1,145,609
Revolving	12,340	12,277
Revolving-Term		825
Loans held for investment, net of fees and costs	3,790,781	3,029,631
Multifamily residential and residential mixed-use | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	94,253	63,595
2020		11,040
2019	25,513	14,486
2018	12,646
2017 and Prior	56,094	11,817
2016 and Prior		26,252
Loans held for investment, net of fees and costs	94,253	63,595
Multifamily residential and residential mixed-use | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	83,210	263,120
2020	12,356	1,501
2019	7,030	35,326
2018	20,396	32,390
2017 and Prior	43,428	54,238
2016 and Prior		137,387
Revolving		2,278
Loans held for investment, net of fees and costs	83,210	263,120
Commercial real estate ("CRE")
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	4,264,519	3,945,948
2022	734,936
2021	874,936	882,483
2020	784,265	851,450
2019	536,450	575,675
2018	330,936	370,839
2017 and Prior	944,121	341,690
2016 and Prior		874,440
Revolving	53,018	43,183
Revolving-Term	5,857	6,188
Loans held for investment, net of fees and costs	4,264,519	3,945,948
Commercial real estate ("CRE") | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	4,163,468	3,719,799
2022	732,046
2021	874,785	872,049
2020	780,530	848,694
2019	495,212	529,182
2018	307,616	306,360
2017 and Prior	914,404	298,904
2016 and Prior		815,239
Revolving	53,018	43,183
Revolving-Term	5,857	6,188
Loans held for investment, net of fees and costs	4,163,468	3,719,799
Commercial real estate ("CRE") | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	64,336	93,792
2022	2,890
2021		6,003
2020		1,024
2019	33,240	39,305
2018	12,720	18,983
2017 and Prior	15,486	11,039
2016 and Prior		17,438
Loans held for investment, net of fees and costs	64,336	93,792
Commercial real estate ("CRE") | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	36,715	132,251
2021	151	4,431
2020	3,735	1,732
2019	7,998	7,082
2018	10,600	45,496
2017 and Prior	14,231	31,747
2016 and Prior		41,763
Loans held for investment, net of fees and costs	36,715	132,251
Commercial real estate ("CRE") | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans		106
2019		106
Loans held for investment, net of fees and costs		106
Acquisition, development, and construction
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	241,019	322,628
2022	25,431
2021	144,151	142,123
2020	18,088	77,427
2019	20,043	56,885
2018	6,349	36,956
2017 and Prior	2,573	6,809
2016 and Prior		774
Revolving	24,097	1,066
Revolving-Term	287	588
Loans held for investment, net of fees and costs	241,019	322,628
Acquisition, development, and construction | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	240,362	307,960
2022	25,431
2021	143,494	142,123
2020	18,088	76,259
2019	20,043	56,885
2018	6,349	23,456
2017 and Prior	2,573	6,809
2016 and Prior		774
Revolving	24,097	1,066
Revolving-Term	287	588
Loans held for investment, net of fees and costs	240,362	307,960
Acquisition, development, and construction | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans		1,078
2020		1,078
Loans held for investment, net of fees and costs		1,078
Acquisition, development, and construction | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	657	13,590
2021	657
2020		90
2018		13,500
Loans held for investment, net of fees and costs	657	13,590
Commercial and Industrial ("C&I") Loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	912,151	933,559
2022	85,944
2021	50,691	94,754
2020	72,606	130,281
2019	52,637	69,112
2018	42,691	58,588
2017 and Prior	50,930	50,762
2016 and Prior		26,511
Revolving	534,298	478,904
Revolving-Term	22,354	24,647
Loans held for investment, net of fees and costs	912,151	933,559
Commercial and Industrial ("C&I") Loans | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	829,961	833,594
2022	76,688
2021	49,878	93,802
2020	64,244	121,291
2019	40,383	53,116
2018	39,283	49,634
2017 and Prior	34,835	36,238
2016 and Prior		23,615
Revolving	513,193	446,134
Revolving-Term	11,457	9,764
Loans held for investment, net of fees and costs	829,961	833,594
Commercial and Industrial ("C&I") Loans | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	17,092	9,203
2022	4,340
2020	942	1,625
2019	287	239
2018	1,642	2,191
2017 and Prior	908	585
2016 and Prior		52
Revolving	8,470	3,225
Revolving-Term	503	1,286
Loans held for investment, net of fees and costs	17,092	9,203
Commercial and Industrial ("C&I") Loans | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	45,264	65,764
2022	4,916
2021	401	402
2020	7,420	5,744
2019	3,635	5,789
2018	1,014	6,011
2017 and Prior	4,849	2,832
2016 and Prior		2,844
Revolving	12,635	28,545
Revolving-Term	10,394	13,597
Loans held for investment, net of fees and costs	45,264	65,764
Commercial and Industrial ("C&I") Loans | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	19,834	24,998
2021	412	550
2020		1,621
2019	8,332	9,968
2018	752	752
2017 and Prior	10,338	11,107
Revolving		1,000
Loans held for investment, net of fees and costs	19,834	24,998
Other Loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	8,927	16,898
Loans held for investment, net of fees and costs	8,927	16,898
Other Loans | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	8,927
Loans held for investment, net of fees and costs	8,927
Other Loans | Performing
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans		16,533
Loans held for investment, net of fees and costs		16,533
Other Loans | Performing | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	8,927
Loans held for investment, net of fees and costs	$ 8,927
Other Loans | Non-Accrual
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans		365
Loans held for investment, net of fees and costs		$ 365