LOANS HELD FOR INVESTMENT, NET - Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Credit Risk Profile of Real Estate Loans [Abstract]
Total	$ 10,763,265		$ 10,766,837
Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	131,925		922,902
2023/2022	919,428		2,700,103
2022/2021	2,712,977		1,582,274
2021/2020	1,564,118		954,855
2020/2019	954,980		960,030
2019/2018 and Prior	3,129,516		2,257,567
Revolving	706,798		704,128
Revolving-Term	75,148		60,048
Total	10,194,890		10,141,907
Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023			481
2023/2022	456		53,182
2022/2021	16,844		45,366
2021/2020	45,237		92,825
2020/2019	91,319		27,827
2019/2018 and Prior	80,866		70,219
Revolving	20,788		21,267
Revolving-Term	8,098		26,082
Total	263,608		337,249
Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022			1,857
2022/2021	9,025		2,196
2021/2020	2,802		96,805
2020/2019	85,699		14,483
2019/2018 and Prior	164,323		130,103
Revolving	16,492		15,567
Revolving-Term	20,508		20,167
Total	298,849		281,178
Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2019/2018 and Prior	748		748
Total	748		748
Business loans
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	69,153		259,180
2023/2022	255,930		434,299
2022/2021	417,317		200,169
2021/2020	197,240		165,092
2020/2019	161,212		160,799
2019/2018 and Prior	479,503		339,404
Revolving	669,079		670,394
Revolving-Term	77,528		78,834
Total	2,326,962		2,308,171
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs 2022/2021	80		77
YTD Gross Charge-Offs 2021/2020			38
YTD Gross Charge-Offs 2020/2019			4,166
YTD Gross Charge-Offs 2019/2018 and Prior			2,229
YTD Gross Charge-Offs Revolving	633		5,464
YTD Gross Charge-Offs Revolving-Term	83		3,390
YTD Gross Charge-Offs	796	$ 2,029	15,364
Business loans | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	69,153		258,699
2023/2022	255,474		390,760
2022/2021	392,650		196,790
2021/2020	193,191		144,796
2020/2019	153,026		150,871
2019/2018 and Prior	435,108		305,258
Revolving	631,958		633,719
Revolving-Term	51,322		35,079
Total	2,181,882		2,115,972
Business loans | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023			481
2023/2022	456		41,682
2022/2021	15,642		1,199
2021/2020	1,262		13,567
2020/2019	1,746		7,125
2019/2018 and Prior	10,551		3,150
Revolving	20,629		21,108
Revolving-Term	7,401		25,306
Total	57,687		113,618
Business loans | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022			1,857
2022/2021	9,025		2,180
2021/2020	2,787		6,729
2020/2019	6,440		2,803
2019/2018 and Prior	33,096		30,248
Revolving	16,492		15,567
Revolving-Term	18,805		18,449
Total	86,645		77,833
Business loans | Doubtful
Credit Risk Profile of Real Estate Loans [Abstract]
2019/2018 and Prior	748		748
Total	748		748
One-to-four family residential and cooperative/condominium apartment
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	7,113		170,601
2023/2022	167,096		213,479
2022/2021	210,948		102,684
2021/2020	101,157		70,529
2020/2019	67,202		62,693
2019/2018 and Prior	275,342		221,875
Revolving	31,290		31,364
Revolving-Term	13,187		14,330
Total	873,335		887,555
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]
2024/2023	7,113		170,601
2023/2022	167,096		213,479
2022/2021	210,948		102,684
2021/2020	101,157		69,524
2020/2019	66,202		62,356
2019/2018 and Prior	266,235		213,131
Revolving	31,131		31,205
Revolving-Term	11,444		12,493
Total	861,326		875,473
One-to-four family residential and cooperative/condominium apartment | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2019/2018 and Prior	33		33
Revolving	159		159
Revolving-Term	697		776
Total	889		968
One-to-four family residential and cooperative/condominium apartment | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2021/2020			1,005
2020/2019	1,000		337
2019/2018 and Prior	9,074		8,711
Revolving-Term	1,046		1,061
Total	11,120		11,114
Multifamily residential and residential mixed-use
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	11,137		256,822
2023/2022	256,226		1,340,197
2022/2021	1,341,393		587,686
2021/2020	578,481		316,312
2020/2019	324,466		393,912
2019/2018 and Prior	1,474,984		1,113,081
Revolving	5,550		4,841
Revolving-Term	4,311		4,325
Total	3,996,548		4,017,176
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs 2019/2018 and Prior			2
YTD Gross Charge-Offs			2
Multifamily residential and residential mixed-use | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	11,137		256,822
2023/2022	256,226		1,340,197
2022/2021	1,340,191		578,352
2021/2020	569,200		283,633
2020/2019	291,859		384,937
2019/2018 and Prior	1,339,820		981,820
Revolving	5,550		4,841
Revolving-Term	4,311		4,325
Total	3,818,294		3,834,927
Multifamily residential and residential mixed-use | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2022/2021	1,202		9,334
2021/2020	9,281		3,880
2020/2019	14,403		3,886
2019/2018 and Prior	56,732		64,273
Total	81,618		81,373
Multifamily residential and residential mixed-use | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2021/2020			28,799
2020/2019	18,204		5,089
2019/2018 and Prior	78,432		66,988
Total	96,636		100,876
Non-owner-occupied commercial real estate
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	40,593		220,045
2023/2022	217,651		738,133
2022/2021	737,938		665,134
2021/2020	661,106		582,652
2020/2019	579,118		370,018
2019/2018 and Prior	1,130,405		783,840
Revolving	11,223		11,919
Revolving-Term	7,864		7,926
Total	3,385,898		3,379,667
Non-owner-occupied commercial real estate | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	40,593		220,045
2023/2022	217,651		738,133
2022/2021	737,938		645,246
2021/2020	641,361		447,002
2020/2019	443,893		359,201
2019/2018 and Prior	1,085,387		756,921
Revolving	11,223		11,919
Revolving-Term	7,864		7,926
Total	3,185,910		3,186,393
Non-owner-occupied commercial real estate | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2022/2021			19,872
2021/2020	19,730		75,378
2020/2019	75,170		4,563
2019/2018 and Prior	13,550		2,763
Total	108,450		102,576
Non-owner-occupied commercial real estate | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2022/2021			16
2021/2020	15		60,272
2020/2019	60,055		6,254
2019/2018 and Prior	31,468		24,156
Total	91,538		90,698
Non-owner-occupied commercial real estate | Total real estate loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total	3,385,898		3,379,667
Acquisition, development, and construction ("ADC")
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	3,929		16,735
2023/2022	22,981		29,034
2022/2021	31,250		74,163
2021/2020	74,173		9,900
2020/2019			14,918
2019/2018 and Prior	15,219		437
Revolving	26,936		22,444
Revolving-Term	864		882
Total	175,352		168,513
Acquisition, development, and construction ("ADC") | Pass
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	3,929		16,735
2023/2022	22,981		17,534
2022/2021	31,250		59,202
2021/2020	59,209		9,900
2020/2019			2,665
2019/2018 and Prior	2,966		437
Revolving	26,936		22,444
Revolving-Term	207		225
Total	147,478		129,142
Acquisition, development, and construction ("ADC") | Special Mention
Credit Risk Profile of Real Estate Loans [Abstract]
2023/2022			11,500
2022/2021			14,961
2021/2020	14,964
2020/2019			12,253
Total	14,964		38,714
Acquisition, development, and construction ("ADC") | Substandard
Credit Risk Profile of Real Estate Loans [Abstract]
2019/2018 and Prior	12,253
Revolving-Term	657		657
Total	12,910		657
Other Loans
Credit Risk Profile of Real Estate Loans [Abstract]
Total	5,170		5,755
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs	30	$ 1
Other Loans | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Total	5,170		5,755
Other Loans | Performing | Credit Risk Profile
Credit Risk Profile of Real Estate Loans [Abstract]
Total	5,170		5,755
Excludes Other Loans
Credit Risk Profile of Real Estate Loans [Abstract]
2024/2023	131,925		923,383
2023/2022	919,884		2,755,142
2022/2021	2,738,846		1,629,836
2021/2020	1,612,157		1,144,485
2020/2019	1,131,998		1,002,340
2019/2018 and Prior	3,375,453		2,458,637
Revolving	744,078		740,962
Revolving-Term	103,754		106,297
Total	10,758,095		10,761,082
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
YTD Gross Charge-Offs 2022/2021	80		77
YTD Gross Charge-Offs 2021/2020			38
YTD Gross Charge-Offs 2020/2019			4,166
YTD Gross Charge-Offs 2019/2018 and Prior			2,231
YTD Gross Charge-Offs Revolving	633		5,464
YTD Gross Charge-Offs Revolving-Term	83		3,404
YTD Gross Charge-Offs	$ 796		$ 15,380