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LOANS HELD FOR INVESTMENT, NET - Credit Quality Indicators (Details) - USD ($) $ in Thousands | Dec. 31, 2021 | Dec. 31, 2020
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Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | $ 9,244,661 | $ 5,622,044
2021 | 1,839,501 |
2020 | 1,502,001 |
2019 | 1,289,329 |
2018 | 726,725 |
2017 | 878,430 |
2016 and Prior | 2,356,918 |
Revolving | 588,432 |
Revolving-Term | 46,426 |
Total Loans | 9,227,762 |
Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 1,828,115 |
2020 | 1,473,478 |
2019 | 1,174,655 |
2018 | 606,030 |
2017 | 752,529 |
2016 and Prior | 2,114,512 |
Revolving | 552,538 |
Revolving-Term | 29,902 |
Total Loans | 8,531,759 |
Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 6,003 |
2020 | 15,891 |
2019 | 54,365 |
2018 | 21,926 |
2017 | 23,775 |
2016 and Prior | 45,900 |
Revolving | 4,071 |
Revolving-Term | 2,033 |
Total Loans | 173,964 |
Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 4,833 |
2020 | 11,011 |
2019 | 50,235 |
2018 | 97,994 |
2017 | 91,019 |
2016 and Prior | 196,506 |
Revolving | 30,823 |
Revolving-Term | 14,491 |
Total Loans | 496,912 |
Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 550 |
2020 | 1,621 |
2019 | 10,074 |
2018 | 775 |
2017 | 11,107 |
Revolving | 1,000 |
Total Loans | 25,127 |
Total real estate loans |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 8,294,204 | 4,978,195
Total real estate loans | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 4,681,059
Total real estate loans | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 83,761
Total real estate loans | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 213,375
One-to-four family residential and cooperative/condominium apartment |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 669,282 | 184,989
2021 | 129,679 |
2020 | 89,096 |
2019 | 82,568 |
2018 | 76,726 |
2017 | 80,365 |
2016 and Prior | 145,946 |
Revolving | 50,724 |
Revolving-Term | 14,178 |
Total Loans | 669,282 |
One-to-four family residential and cooperative/condominium apartment | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 183,293
2021 | 129,679 |
2020 | 86,028 |
2019 | 80,195 |
2018 | 75,354 |
2017 | 77,829 |
2016 and Prior | 129,276 |
Revolving | 49,878 |
Revolving-Term | 12,537 |
Total Loans | 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 | 335 |
2018 | 752 |
2017 | 334 |
2016 and Prior | 2,158 |
Revolving | 846 |
Revolving-Term | 747 |
Total Loans | 6,296 |
One-to-four family residential and cooperative/condominium apartment | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 1,696
2020 | 1,944 |
2019 | 2,038 |
2018 | 597 |
2017 | 2,202 |
2016 and Prior | 14,512 |
Revolving-Term | 894 |
Total Loans | 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 | 3,356,346 | 2,758,743
2021 | 590,462 |
2020 | 353,747 |
2019 | 505,089 |
2018 | 183,616 |
2017 | 398,804 |
2016 and Prior | 1,309,248 |
Revolving | 14,555 |
Revolving-Term | 825 |
Total Loans | 3,356,346 |
Multifamily residential and residential mixed-use | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 2,523,258
2021 | 590,462 |
2020 | 341,206 |
2019 | 455,277 |
2018 | 151,226 |
2017 | 332,749 |
2016 and Prior | 1,145,609 |
Revolving | 12,277 |
Revolving-Term | 825 |
Total Loans | 3,029,631 |
Multifamily residential and residential mixed-use | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 56,400
2020 | 11,040 |
2019 | 14,486 |
2017 | 11,817 |
2016 and Prior | 26,252 |
Total Loans | 63,595 |
Multifamily residential and residential mixed-use | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 179,085
2020 | 1,501 |
2019 | 35,326 |
2018 | 32,390 |
2017 | 54,238 |
2016 and Prior | 137,387 |
Revolving | 2,278 |
Total Loans | 263,120 |
Commercial real estate ("CRE") |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 3,945,948 | 1,878,167
2021 | 882,483 |
2020 | 851,450 |
2019 | 575,675 |
2018 | 370,839 |
2017 | 341,690 |
2016 and Prior | 874,439 |
Revolving | 43,183 |
Revolving-Term | 6,188 |
Total Loans | 3,945,947 |
Commercial real estate ("CRE") | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 1,831,712
2021 | 872,049 |
2020 | 848,694 |
2019 | 529,182 |
2018 | 306,360 |
2017 | 298,904 |
2016 and Prior | 815,238 |
Revolving | 43,183 |
Revolving-Term | 6,188 |
Total Loans | 3,719,798 |
Commercial real estate ("CRE") | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 13,861
2021 | 6,003 |
2020 | 1,024 |
2019 | 39,305 |
2018 | 18,983 |
2017 | 11,039 |
2016 and Prior | 17,438 |
Total Loans | 93,792 |
Commercial real estate ("CRE") | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 32,594
2021 | 4,431 |
2020 | 1,732 |
2019 | 7,082 |
2018 | 45,496 |
2017 | 31,747 |
2016 and Prior | 41,763 |
Total Loans | 132,251 |
Commercial real estate ("CRE") | Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2019 | 106 |
Total Loans | 106 |
Acquisition, development, and construction ("ADC") |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 322,628 | 156,296
2021 | 142,123 |
2020 | 77,427 |
2019 | 56,885 |
2018 | 36,956 |
2017 | 6,809 |
2016 and Prior | 774 |
Revolving | 1,066 |
Revolving-Term | 588 |
Total Loans | 322,628 |
Acquisition, development, and construction ("ADC") | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 142,796
2021 | 142,123 |
2020 | 76,259 |
2019 | 56,885 |
2018 | 23,456 |
2017 | 6,809 |
2016 and Prior | 774 |
Revolving | 1,066 |
Revolving-Term | 588 |
Total Loans | 307,960 |
Acquisition, development, and construction ("ADC") | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 13,500
2020 | 1,078 |
Total Loans | 1,078 |
Acquisition, development, and construction ("ADC") | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2020 | 90 |
2018 | 13,500 |
Total Loans | 13,590 |
Commercial and Industrial ("C&I") Loans |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 933,559 | 641,533
2021 | 94,754 |
2020 | 130,281 |
2019 | 69,112 |
2018 | 58,588 |
2017 | 50,762 |
2016 and Prior | 26,511 |
Revolving | 478,904 |
Revolving-Term | 24,647 |
Total Loans | 933,559 |
Commercial and Industrial ("C&I") Loans | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 613,691
2021 | 93,802 |
2020 | 121,291 |
2019 | 53,116 |
2018 | 49,634 |
2017 | 36,238 |
2016 and Prior | 23,615 |
Revolving | 446,134 |
Revolving-Term | 9,764 |
Total Loans | 833,594 |
Commercial and Industrial ("C&I") Loans | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 2,131
2020 | 1,625 |
2019 | 239 |
2018 | 2,191 |
2017 | 585 |
2016 and Prior | 52 |
Revolving | 3,225 |
Revolving-Term | 1,286 |
Total Loans | 9,203 |
Commercial and Industrial ("C&I") Loans | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 13,315
2021 | 402 |
2020 | 5,744 |
2019 | 5,789 |
2018 | 6,011 |
2017 | 2,832 |
2016 and Prior | 2,844 |
Revolving | 28,545 |
Revolving-Term | 13,597 |
Total Loans | 65,764 |
Commercial and Industrial ("C&I") Loans | Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 12,396
2021 | 550 |
2020 | 1,621 |
2019 | 9,968 |
2018 | 752 |
2017 | 11,107 |
Revolving | 1,000 |
Total Loans | 24,998 |
Commercial and Industrial ("C&I") Loans | Total real estate loans |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 5,619,728
Commercial and Industrial ("C&I") Loans | Total real estate loans | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 5,294,750
Commercial and Industrial ("C&I") Loans | Total real estate loans | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 85,892
Commercial and Industrial ("C&I") Loans | Total real estate loans | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 226,690
Commercial and Industrial ("C&I") Loans | Total real estate loans | Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 12,396
Other Loans |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 16,898 | 2,316
Other Loans | Credit Risk Profile |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 16,898 |
Other Loans | Performing |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 2,315
Other Loans | Performing | Credit Risk Profile |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 16,533 |
Other Loans | Non-Accrual |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | $ 1
Other Loans | Non-Accrual | Credit Risk Profile |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | $ 365 |

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