LOANS HELD FOR INVESTMENT, NET - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	$ 9,660,907	$ 9,244,661
2022	1,401,882
2021	1,762,601	1,839,501
2020	1,348,692	1,502,001
2019	1,141,101	1,289,329
2018	654,352	726,725
2017 and Prior	2,616,737	878,430
2016 and Prior		2,356,918
Revolving	686,171	588,432
Revolving-Term	38,582	46,426
Total Loans	9,650,118	9,227,762
Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2022	1,389,994
2021	1,760,706	1,828,115
2020	1,322,185	1,473,478
2019	1,046,787	1,174,655
2018	578,869	606,030
2017 and Prior	2,423,540	752,529
2016 and Prior		2,114,512
Revolving	656,061	552,538
Revolving-Term	27,282	29,902
Total Loans	9,205,424	8,531,759
Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2022	7,375
2021		6,003
2020	2,682	15,891
2019	62,113	54,365
2018	17,633	21,926
2017 and Prior	62,218	23,775
2016 and Prior		45,900
Revolving	13,373	4,071
Revolving-Term	1,314	2,033
Total Loans	166,708	173,964
Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2022	4,513
2021	1,404	4,833
2020	23,825	11,011
2019	23,649	50,235
2018	57,098	97,994
2017 and Prior	120,180	91,019
2016 and Prior		196,506
Revolving	16,737	30,823
Revolving-Term	9,986	14,491
Total Loans	257,392	496,912
Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2021	491	550
2020		1,621
2019	8,552	10,074
2018	752	775
2017 and Prior	10,799	11,107
Revolving		1,000
Total Loans	20,594	25,127
Total real estate loans
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	8,689,230	8,294,204
One-to-four family residential and cooperative/condominium apartment
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	691,586	669,282
2022	109,116
2021	111,694	129,679
2020	76,909	89,096
2019	68,125	82,568
2018	69,562	76,726
2017 and Prior	195,127	80,365
2016 and Prior		145,946
Revolving	48,228	50,724
Revolving-Term	12,825	14,178
Total Loans	691,586	669,282
One-to-four family residential and cooperative/condominium apartment | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2022	109,116
2021	111,694	129,679
2020	75,873	86,028
2019	66,563	80,195
2018	68,407	75,354
2017 and Prior	178,745	77,829
2016 and Prior		129,276
Revolving	47,383	49,878
Revolving-Term	11,294	12,537
Total Loans	669,075	640,776
One-to-four family residential and cooperative/condominium apartment | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2020		1,124
2019	332	335
2018	744	752
2017 and Prior	1,519	334
2016 and Prior		2,158
Revolving	845	846
Revolving-Term	737	747
Total Loans	4,177	6,296
One-to-four family residential and cooperative/condominium apartment | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2020	1,036	1,944
2019	1,230	2,038
2018	411	597
2017 and Prior	14,863	2,202
2016 and Prior		14,512
Revolving-Term	794	894
Total Loans	18,334	22,187
One-to-four family residential and cooperative/condominium apartment | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2018		23
Total Loans		23
Multifamily residential and residential mixed-use
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	3,654,164	3,356,346
2022	770,923
2021	588,984	590,462
2020	340,244	353,747
2019	430,385	505,089
2018	162,829	183,616
2017 and Prior	1,347,607	398,804
2016 and Prior		1,309,248
Revolving	12,372	14,555
Revolving-Term	820	825
Total Loans	3,654,164	3,356,346
Multifamily residential and residential mixed-use | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2022	770,923
2021	588,984	590,462
2020	327,826	341,206
2019	392,724	455,277
2018	128,595	151,226
2017 and Prior	1,215,756	332,749
2016 and Prior		1,145,609
Revolving	12,372	12,277
Revolving-Term	820	825
Total Loans	3,438,000	3,029,631
Multifamily residential and residential mixed-use | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2020		11,040
2019	28,066	14,486
2018	9,696
2017 and Prior	42,783	11,817
2016 and Prior		26,252
Total Loans	80,545	63,595
Multifamily residential and residential mixed-use | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2020	12,418	1,501
2019	9,595	35,326
2018	24,538	32,390
2017 and Prior	89,068	54,238
2016 and Prior		137,387
Revolving		2,278
Total Loans	135,619	263,120
Commercial real estate ("CRE")
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	4,091,372	3,945,948
2022	459,162
2021	879,604	882,483
2020	788,722	851,450
2019	558,219	575,675
2018	357,667	370,839
2017 and Prior	1,001,394	341,690
2016 and Prior		874,439
Revolving	40,757	43,183
Revolving-Term	5,847	6,188
Total Loans	4,091,372	3,945,947
Commercial real estate ("CRE") | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2022	456,248
2021	879,453	872,049
2020	784,966	848,694
2019	517,168	529,182
2018	321,183	306,360
2017 and Prior	973,378	298,904
2016 and Prior		815,238
Revolving	40,757	43,183
Revolving-Term	5,847	6,188
Total Loans	3,979,000	3,719,798
Commercial real estate ("CRE") | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2022	2,914
2021		6,003
2020		1,024
2019	33,389	39,305
2018	7,128	18,983
2017 and Prior	16,899	11,039
2016 and Prior		17,438
Total Loans	60,330	93,792
Commercial real estate ("CRE") | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2021	151	4,431
2020	3,756	1,732
2019	7,662	7,082
2018	29,356	45,496
2017 and Prior	11,117	31,747
2016 and Prior		41,763
Total Loans	52,042	132,251
Commercial real estate ("CRE") | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2019		106
Total Loans		106
Acquisition, development, and construction
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	252,108	322,628
2022	8,413
2021	127,808	142,123
2020	59,294	77,427
2019	25,709	56,885
2018	17,543	36,956
2017 and Prior	4,099	6,809
2016 and Prior		774
Revolving	8,788	1,066
Revolving-Term	454	588
Total Loans	252,108	322,628
Acquisition, development, and construction | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2022	8,413
2021	127,151	142,123
2020	59,294	76,259
2019	25,709	56,885
2018	17,543	23,456
2017 and Prior	4,099	6,809
2016 and Prior		774
Revolving	8,788	1,066
Revolving-Term	454	588
Total Loans	251,451	307,960
Acquisition, development, and construction | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2020		1,078
Total Loans		1,078
Acquisition, development, and construction | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2021	657
2020		90
2018		13,500
Total Loans	657	13,590
Commercial and Industrial ("C&I") Loans
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	960,888	933,559
2022	54,268
2021	54,511	94,754
2020	83,523	130,281
2019	58,663	69,112
2018	46,751	58,588
2017 and Prior	68,510	50,762
2016 and Prior		26,511
Revolving	576,026	478,904
Revolving-Term	18,636	24,647
Total Loans	960,888	933,559
Commercial and Industrial ("C&I") Loans | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2022	45,294
2021	53,424	93,802
2020	74,226	121,291
2019	44,623	53,116
2018	43,141	49,634
2017 and Prior	51,562	36,238
2016 and Prior		23,615
Revolving	546,761	446,134
Revolving-Term	8,867	9,764
Total Loans	867,898	833,594
Commercial and Industrial ("C&I") Loans | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2022	4,461
2020	2,682	1,625
2019	326	239
2018	65	2,191
2017 and Prior	1,017	585
2016 and Prior		52
Revolving	12,528	3,225
Revolving-Term	577	1,286
Total Loans	21,656	9,203
Commercial and Industrial ("C&I") Loans | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2022	4,513
2021	596	402
2020	6,615	5,744
2019	5,162	5,789
2018	2,793	6,011
2017 and Prior	5,132	2,832
2016 and Prior		2,844
Revolving	16,737	28,545
Revolving-Term	9,192	13,597
Total Loans	50,740	65,764
Commercial and Industrial ("C&I") Loans | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2021	491	550
2020		1,621
2019	8,552	9,968
2018	752	752
2017 and Prior	10,799	11,107
Revolving		1,000
Total Loans	20,594	24,998
Other Loans
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	10,789	16,898
Other Loans | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	10,789
Other Loans | Performing
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding		16,533
Other Loans | Performing | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	10,658
Other Loans | Non-Accrual
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding		$ 365
Other Loans | Non-Accrual | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Principal balances outstanding	$ 131