FAIR VALUE MEASUREMENT - FV of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Assets:
Other assets - GNMA EBO loans	$ 7,340,309	$ 7,382,404
Carrying Value
Assets:
Cash and cash equivalents	218,731	215,664
Investment securities HTM	2,336	2,371
LHFI	7,339,023	7,381,124
Federal Home Loan Bank stock	77,725	55,293
Liabilities:
Certificates of deposit	3,197,973	3,227,954
Borrowings	1,886,000	1,745,000
Long-term debt	224,948	224,766
Fair Value
Assets:
Cash and cash equivalents	218,731	215,664
Investment securities HTM	2,291	2,331
LHFI	6,909,608	7,002,028
Federal Home Loan Bank stock	77,725	55,293
Liabilities:
Certificates of deposit	3,185,782	3,216,665
Borrowings	1,878,834	1,750,023
Long-term debt	174,418	132,996
Multifamily | Carrying Value
Assets:
LHFS – multifamily and other	7,634	6,788
Mortgage servicing rights – multifamily and SBA	27,583	29,987
Multifamily | Fair Value
Assets:
LHFS – multifamily and other	7,654	6,871
Mortgage servicing rights – multifamily and SBA	33,148	35,292
Other assets - GNMA EBO loans | Carrying Value
Assets:
Other assets - GNMA EBO loans	5,747	5,617
Other assets - GNMA EBO loans | Fair Value
Assets:
Other assets - GNMA EBO loans	5,747	5,617
Level 1 | Fair Value
Assets:
Cash and cash equivalents	218,731	215,664
Investment securities HTM	0	0
LHFI	0	0
Federal Home Loan Bank stock	0	0
Liabilities:
Certificates of deposit	0	0
Borrowings		0
Long-term debt	0	0
Level 1 | Multifamily | Fair Value
Assets:
LHFS – multifamily and other	0	0
Mortgage servicing rights – multifamily and SBA	0	0
Level 1 | Other assets - GNMA EBO loans | Fair Value
Assets:
Other assets - GNMA EBO loans	0	0
Level 2 | Fair Value
Assets:
Cash and cash equivalents	0	0
Investment securities HTM	2,291	2,331
LHFI	0	0
Federal Home Loan Bank stock	77,725	55,293
Liabilities:
Certificates of deposit	3,185,782	3,216,665
Borrowings	1,878,834	1,750,023
Long-term debt	174,418	132,996
Level 2 | Multifamily | Fair Value
Assets:
LHFS – multifamily and other	7,654	6,871
Mortgage servicing rights – multifamily and SBA	0	0
Level 2 | Other assets - GNMA EBO loans | Fair Value
Assets:
Other assets - GNMA EBO loans	0	0
Level 3 | Fair Value
Assets:
Cash and cash equivalents	0	0
Investment securities HTM	0	0
LHFI	6,909,608	7,002,028
Federal Home Loan Bank stock	0	0
Liabilities:
Certificates of deposit	0	0
Borrowings		0
Long-term debt	0	0
Level 3 | Multifamily | Fair Value
Assets:
LHFS – multifamily and other	0	0
Mortgage servicing rights – multifamily and SBA	33,148	35,292
Level 3 | Other assets - GNMA EBO loans | Fair Value
Assets:
Other assets - GNMA EBO loans	$ 5,747	$ 5,617