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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 01, 2021 $ / shares shares | Sep. 30, 2021 item | Dec. 31, 2021 USD ($) segment item $ / shares | Jan. 01, 2021 USD ($) | Dec. 31, 2020 USD ($) $ / shares | Dec. 31, 2019 USD ($) | Jan. 01, 2019 USD ($) | Dec. 31, 2018 USD ($)
Common stock, par value (in dollars per share) | $ / shares | $ 0.01 |  | $ 0.01 |  | $ 0.01 |  |  |
Common stock converted into right to receive shares (in shares) | shares | 0.6480 |  |  |  |  |  |  |
Preferred stock, Series A, par value (in dollars per share) | $ / shares | $ 0.01 |  | $ 0.01 |  | $ 0.01 |  |  |
Number of branch locations | item |  |  | 60 |  |  |  |  |
Number Of Real Estate Investments Dissolved | item |  | 2 |  |  |  |  |  |
Operating right-of-use assets |  |  | $ 64,258 |  | $ 33,898 |  | $ 41,600 |
Operating lease liabilities |  |  | 66,103 |  | 39,874 |  | $ 41,600 |
Unrecognized Tax Benefits |  |  | $ 0 |  | 0 |  |  |
Number of Reportable Segments | segment |  |  | 1 |  |  |  |  |
Number of Operating Segments | segment |  |  | 1 |  |  |  |  |
Allowance for credit losses |  |  | $ 83,853 |  | 41,461 | $ 28,441 |  | $ 21,782
Collectively evaluated for impairment |  |  | 8,980,000 |  | 5,604,975 |  |  |
Collectively evaluated for impairment, allowance |  |  | 41,400 |  | 34,987 |  |  |
Individually evaluated for impairment |  |  | 51,400 |  | 17,069 |  |  |
Individually evaluated for impairment, allowance |  |  | 22,300 |  | 6,474 |  |  |
Pooled PCD loans, allowance for credit loss |  |  | 6,200 |  |  |  |  |
Retained earnings |  |  | $ 654,726 |  | 600,641 |  |  |
Core deposits |  |  |  |  |  |  |  |
Intangible Asset Useful Life |  |  | 10 years |  |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  |  |  | (3,919) |  |  |
Maximum | Furniture Fixtures And Equipment [Member] |  |  |  |  |  |  |  |
Property Plant and Equipment Useful Life |  |  | 10 years |  |  |  |  |
Minimum | Furniture Fixtures And Equipment [Member] |  |  |  |  |  |  |  |
Property Plant and Equipment Useful Life |  |  | 3 years |  |  |  |  |
Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  | $ (3,900) |  |  |  |  |
Reserve for unfunded commitments |  |  | 1,400 |  |  |  |  |
Retained earnings |  |  |  | $ 1,700 |  |  |  |
PCD loans |  |  |  |  |  |  |  |
Individually evaluated for impairment |  |  | 75,200 |  |  |  |  |
Individually evaluated for impairment, allowance |  |  | 13,900 |  |  |  |  |
Pooled PCD loans |  |  | 138,300 |  |  |  |  |
One-to-four family residential and cooperative/condominium apartment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  | 5,932 |  | 644 | 269 |  | 198
Collectively evaluated for impairment |  |  |  |  | 184,989 |  |  |
Collectively evaluated for impairment, allowance |  |  |  |  | 644 |  |  |
One-to-four family residential and cooperative/condominium apartment | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  |  |  | 1,048 |  |  |
Multifamily residential and residential mixed-use |  |  |  |  |  |  |  |
Allowance for credit losses |  |  | 7,816 |  | 17,016 | 10,142 |  | 13,446
Collectively evaluated for impairment |  |  |  |  | 2,756,880 |  |  |
Collectively evaluated for impairment, allowance |  |  |  |  | 17,016 |  |  |
Individually evaluated for impairment |  |  |  |  | 1,863 |  |  |
Multifamily residential and residential mixed-use | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  |  |  | (8,254) |  |  |
Commercial real estate ("CRE") |  |  |  |  |  |  |  |
Allowance for credit losses |  |  | 29,166 |  | 9,059 | 3,900 |  | 3,777
Collectively evaluated for impairment |  |  |  |  | 1,875,463 |  |  |
Collectively evaluated for impairment, allowance |  |  |  |  | 9,059 |  |  |
Individually evaluated for impairment |  |  |  |  | 2,704 |  |  |
Commercial real estate ("CRE") | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  |  |  | 4,849 |  |  |
Commercial and Industrial ("C&I") Loans |  |  |  |  |  |  |  |
Allowance for credit losses |  |  | 35,331 |  | 12,737 | 12,870 |  | 3,946
Collectively evaluated for impairment |  |  |  |  | 629,031 |  |  |
Collectively evaluated for impairment, allowance |  |  |  |  | 6,263 |  |  |
Individually evaluated for impairment |  |  |  |  | 12,502 |  |  |
Individually evaluated for impairment, allowance |  |  |  |  | 6,474 |  |  |
Commercial and Industrial ("C&I") Loans | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  |  |  | (1,935) |  |  |
Other Loans |  |  |  |  |  |  |  |
Allowance for credit losses |  |  | $ 751 |  | 12 | $ 16 |  | $ 18
Collectively evaluated for impairment |  |  |  |  | 2,316 |  |  |
Collectively evaluated for impairment, allowance |  |  |  |  | 12 |  |  |
Other Loans | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |
Allowance for credit losses |  |  |  |  | $ (8) |  |  |

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