LOANS HELD FOR INVESTMENT, NET - Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	$ 10,850,611		$ 10,850,611		$ 10,566,831
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs 2022/2021					477
YTD Gross Charge-Offs 2021/2020			77		4,720
YTD Gross Charge-Offs 2020/2019			38		2,088
YTD Gross Charge-Offs 2019/2018			4,166
YTD Gross Charge-Offs 2018 and Prior/2017 and Prior			2,231		2,414
YTD Gross Charge-Offs Revolving			1,021		1,460
YTD Gross Charge-Offs Revolving-Term			3,404		242
YTD Gross Charge-Offs			10,937		11,401
Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	808,171		808,171
2022/2021	2,793,493		2,793,493		2,845,428
2021/2020	1,640,908		1,640,908		1,733,872
2020/2019	1,009,045		1,009,045		1,196,053
2019/2018	986,544		986,544		1,024,753
2018/2017 and Prior	2,401,398		2,401,398		522,005
2016 and Prior					2,175,148
Revolving	721,788		721,788		726,712
Revolving-Term	64,405		64,405		59,849
Total Loans	10,425,752		10,425,752		10,283,820
Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	506		506
2022/2021	3,184		3,184		6,634
2021/2020	20,459		20,459
2020/2019	101,118		101,118		20,549
2019/2018	13,340		13,340		17,364
2018/2017 and Prior	59,530		59,530		16,628
2016 and Prior					31,664
Revolving	23,121		23,121		9,641
Revolving-Term	9,835		9,835		1,204
Total Loans	231,093		231,093		103,684
Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	1		1
2022/2021	1,950		1,950		5,242
2021/2020	3,118		3,118		2,052
2020/2019	44,251		44,251		23,233
2019/2018	15,349		15,349		19,143
2018/2017 and Prior	100,553		100,553		22,819
2016 and Prior					66,232
Revolving	8,290		8,290		11,290
Revolving-Term	9,072		9,072		10,505
Total Loans	182,584		182,584		160,516
Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2019/2018	4,166		4,166		8,332
2018/2017 and Prior	749		749		752
2016 and Prior					2,048
Total Loans	4,915		4,915		11,132
Excludes Other Loans
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	808,678		808,678
2022/2021	2,798,627		2,798,627		2,857,304
2021/2020	1,664,485		1,664,485		1,735,924
2020/2019	1,154,414		1,154,414		1,239,835
2019/2018	1,019,399		1,019,399		1,069,592
2018/2017 and Prior	2,562,230		2,562,230		562,204
2016 and Prior					2,275,092
Revolving	753,199		753,199		747,643
Revolving-Term	83,312		83,312		71,558
Total Loans	10,844,344		10,844,344		10,559,152
Business loans
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	198,338		198,338
2022/2021	433,722		433,722		461,575
2021/2020	203,331		203,331		229,523
2020/2019	175,594		175,594		197,259
2019/2018	170,837		170,837		188,094
2018/2017 and Prior	361,288		361,288		149,322
2016 and Prior					261,330
Revolving	672,232		672,232		671,312
Revolving-Term	56,426		56,426		53,442
Total Loans	2,271,768		2,271,768		2,211,857
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs 2022/2021					477
YTD Gross Charge-Offs 2021/2020			77		4,720
YTD Gross Charge-Offs 2020/2019			38		2,088
YTD Gross Charge-Offs 2019/2018			4,166
YTD Gross Charge-Offs 2018 and Prior/2017 and Prior			2,229		2,414
YTD Gross Charge-Offs Revolving			1,021		1,460
YTD Gross Charge-Offs Revolving-Term			3,390		242
YTD Gross Charge-Offs	5,147	$ 5,462	10,921	$ 8,742	11,401
Business loans | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	197,831		197,831
2022/2021	428,588		428,588		449,699
2021/2020	199,606		199,606		228,143
2020/2019	167,826		167,826		187,522
2019/2018	159,084		159,084		173,527
2018/2017 and Prior	316,910		316,910		130,576
2016 and Prior					240,131
Revolving	640,980		640,980		650,960
Revolving-Term	39,015		39,015		43,552
Total Loans	2,149,840		2,149,840		2,104,110
Business loans | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	506		506
2022/2021	3,184		3,184		6,634
2021/2020	1,279		1,279
2020/2019	923		923		894
2019/2018	4,850		4,850		1,529
2018/2017 and Prior	13,541		13,541		15,893
2016 and Prior					4,213
Revolving	22,962		22,962		9,062
Revolving-Term	9,125		9,125		478
Total Loans	56,370		56,370		38,703
Business loans | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	1		1
2022/2021	1,950		1,950		5,242
2021/2020	2,446		2,446		1,380
2020/2019	6,845		6,845		8,843
2019/2018	2,737		2,737		4,706
2018/2017 and Prior	30,088		30,088		2,101
2016 and Prior					14,938
Revolving	8,290		8,290		11,290
Revolving-Term	8,286		8,286		9,412
Total Loans	60,643		60,643		57,912
Business loans | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2019/2018	4,166		4,166		8,332
2018/2017 and Prior	749		749		752
2016 and Prior					2,048
Total Loans	4,915		4,915		11,132
One-to-four family residential and cooperative/condominium apartment
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	161,750		161,750
2022/2021	217,184		217,184		225,031
2021/2020	103,310		103,310		108,185
2020/2019	70,929		70,929		73,758
2019/2018	64,517		64,517		66,742
2018/2017 and Prior	227,440		227,440		67,180
2016 and Prior					176,292
Revolving	33,418		33,418		41,751
Revolving-Term	14,321		14,321		14,382
Total Loans	892,869		892,869		773,321
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs Revolving-Term			14
YTD Gross Charge-Offs			14
One-to-four family residential and cooperative/condominium apartment | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	161,750		161,750
2022/2021	217,184		217,184		225,031
2021/2020	103,310		103,310		108,185
2020/2019	69,919		69,919		72,732
2019/2018	63,299		63,299		65,515
2018/2017 and Prior	215,385		215,385		66,038
2016 and Prior					164,338
Revolving	33,259		33,259		41,172
Revolving-Term	12,825		12,825		12,563
Total Loans	876,931		876,931		755,574
One-to-four family residential and cooperative/condominium apartment | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2018/2017 and Prior	756		756		735
2016 and Prior					1,175
Revolving	159		159		579
Revolving-Term	710		710		726
Total Loans	1,625		1,625		3,215
One-to-four family residential and cooperative/condominium apartment | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2020/2019	1,010		1,010		1,026
2019/2018	1,218		1,218		1,227
2018/2017 and Prior	11,299		11,299		407
2016 and Prior					10,779
Revolving-Term	786		786		1,093
Total Loans	14,313		14,313		14,532
Multifamily residential and residential mixed-use
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	244,041		244,041
2022/2021	1,367,753		1,367,753		1,386,549
2021/2020	593,271		593,271		582,393
2020/2019	318,024		318,024		328,718
2019/2018	398,615		398,615		414,117
2018/2017 and Prior	1,163,265		1,163,265		147,385
2016 and Prior					1,155,080
Revolving	12,715		12,715		12,584
Revolving-Term	4,340		4,340
Total Loans	4,102,024		4,102,024		4,026,826
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs 2018 and Prior/2017 and Prior			2
YTD Gross Charge-Offs	2		2
Multifamily residential and residential mixed-use | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	244,041		244,041
2022/2021	1,367,753		1,367,753		1,386,549
2021/2020	589,048		589,048		582,393
2020/2019	285,272		285,272		316,424
2019/2018	389,601		389,601		395,933
2018/2017 and Prior	1,086,015		1,086,015		127,074
2016 and Prior					1,107,281
Revolving	12,715		12,715		12,584
Revolving-Term	4,340		4,340
Total Loans	3,978,785		3,978,785		3,928,238
Multifamily residential and residential mixed-use | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2021/2020	4,223		4,223
2020/2019	22,096		22,096
2019/2018	3,905		3,905		11,183
2018/2017 and Prior	30,476		30,476
2016 and Prior					14,168
Total Loans	60,700		60,700		25,351
Multifamily residential and residential mixed-use | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2020/2019	10,656		10,656		12,294
2019/2018	5,109		5,109		7,001
2018/2017 and Prior	46,774		46,774		20,311
2016 and Prior					33,631
Total Loans	62,539		62,539		73,237
Non-owner-occupied commercial real estate
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	196,881		196,881
2022/2021	728,514		728,514		747,272
2021/2020	667,914		667,914		662,623
2020/2019	582,220		582,220		628,858
2019/2018	369,786		369,786		384,696
2018/2017 and Prior	809,742		809,742		198,317
2016 and Prior					680,303
Revolving	11,237		11,237		11,963
Revolving-Term	7,987		7,987		3,453
Total Loans	3,374,281		3,374,281		3,317,485
Non-owner-occupied commercial real estate | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	196,881		196,881
2022/2021	728,514		728,514		747,272
2021/2020	667,899		667,899		662,608
2020/2019	478,381		478,381		608,133
2019/2018	358,916		358,916		373,835
2018/2017 and Prior	782,593		782,593		198,317
2016 and Prior					661,311
Revolving	11,237		11,237		11,963
Revolving-Term	7,987		7,987		3,453
Total Loans	3,232,408		3,232,408		3,266,892
Non-owner-occupied commercial real estate | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2020/2019	78,099		78,099		19,655
2019/2018	4,585		4,585		4,652
2018/2017 and Prior	14,757		14,757
2016 and Prior					12,108
Total Loans	97,441		97,441		36,415
Non-owner-occupied commercial real estate | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2021/2020	15		15		15
2020/2019	25,740		25,740		1,070
2019/2018	6,285		6,285		6,209
2018/2017 and Prior	12,392		12,392
2016 and Prior					6,884
Total Loans	44,432		44,432		14,178
Non-owner-occupied commercial real estate | Total real estate loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	3,374,281		3,374,281		3,317,485
Acquisition, development, and construction ("ADC")
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	7,668		7,668
2022/2021	51,454		51,454		36,877
2021/2020	96,659		96,659		153,200
2020/2019	7,647		7,647		11,242
2019/2018	15,644		15,644		15,943
2018/2017 and Prior	495		495
2016 and Prior					2,087
Revolving	23,597		23,597		10,033
Revolving-Term	238		238		281
Total Loans	203,402		203,402		229,663
Acquisition, development, and construction ("ADC") | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022	7,668		7,668
2022/2021	51,454		51,454		36,877
2021/2020	81,045		81,045		152,543
2020/2019	7,647		7,647		11,242
2019/2018	15,644		15,644		15,943
2018/2017 and Prior	495		495
2016 and Prior					2,087
Revolving	23,597		23,597		10,033
Revolving-Term	238		238		281
Total Loans	187,788		187,788		229,006
Acquisition, development, and construction ("ADC") | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2021/2020	14,957		14,957
Total Loans	14,957		14,957
Acquisition, development, and construction ("ADC") | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2021/2020	657		657		657
Total Loans	657		657		657
Other Loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	6,267		6,267		7,679
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs	26	$ 49	60	$ 52
Other Loans | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	6,267		6,267		7,679
Other Loans | Performing | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	6,048		6,048		7,580
Other Loans | Non-Accrual | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Total Loans	$ 219		$ 219		$ 99