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Borrowings - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Short Term And Long Term Debt [Line Items]
FHLB advances	$ 2,090.0
Unencumbered securities	647.5
Multifamily loans held as collateral	1,440.0
Repurchase agreements | Mortgage-backed securities
Schedule Of Short Term And Long Term Debt [Line Items]
Mortgage-backed securities amortized cost	52.6	$ 88.9
Mortgage-backed securities held for sale fair value	$ 53.8	$ 91.4

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Additional Funding Federal Home Loan Bank Advances Long Term

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Multifamily Loans Held As Collateral by Federal Home Loan Bank.

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Schedule Of Short Term And Long Term Debt [Line Items]

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Unencumbered Securities

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Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as held-to-maturity.

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